Embassies in Yemen Close as Security Forces Step Up Offensive Against Al Qaeda

President Obama returned today from his vacation in Hawaii as the United States steps up air travel security and refocuses its attention on Yemen, where threats from al Qaeda groups have forced several embassies to close.

The U.S. embassy in Yemen's capital city of San'a was closed for a second straight day because of ongoing threats by al Qaeda. Secretary of State Hillary Clinton today said these threats predate this holiday season, and added that the embassy will open "when security conditions permit."

Video of Hillary Clinton addressing U.S. relations with Yemen.Play
Clinton: US Embassy in Yemen Closed Due to Threats

United States officials are not alone in their concerns about an imminent al Qaeda threat in Yemen. Japan also closed its embassy, as did the British for unspecified "security reasons."

Security at the embassies and other potential Western targets in Yemen is tighter than ever as fears of an attack mount.

Yemen has been the site of suspected terror activity for some time. In September 2008, twin suicide car bombs at the U.S. embassy killed more than a dozen people. But officials suspect a new attack could be worse. Intelligence indicates that four or five suicide bombers are in the "operational stage," either on their way or already heading for targets inside San'a, according to U.S. officials.

VIDEO: Washington Post reporter Bob Woodward discusses national security challenges.Play

On Dec. 17, Yemeni security forces managed to kill three suicide bombers and find a vest of a fourth. But officials believe different suicide bombers have been trained for new attacks.

A U.S. official tells ABC News that it is believed that Umar Abdulmutallab, the 23-year-old who planned to blow up U.S.-bound Northwest Flight 253, was trained and equipped at the same al Qaeda in the Arabian Peninsula training camp in Abyan that was struck by U.S. cruise missiles, and then followed by an attack from Yemeni ground forces, on Dec. 17th.

The clampdown on terror suspects has already begun in the volatile Arab country. Just outside of the capital, government forces clashed with al Qaeda militants and officials said several had been killed.

VIDEO: U.S. Gen. David Petraeus promises to deliver aid to Yemen government.Play

Yemeni forces in San'a today went after Nazil al Hanq, a key leader of the Al Qaeda in the Arabian Peninsula, which claimed responsibility for the botched Christmas Day terror plot to blow up a Detroit-bound airline. Al Hanq would be a big catch for the Yemenis because they believe he was one of the men behind plans by al Qaeda to blow up Western or Yemeni government targets. But even though security forces killed two men close to him in the firefight, they were unable to get al Hanq. Embassies are likely to stay closed until further notice.

Until the past few weeks, Yemeni forces had been focusing specifically on rebel group al Houthi in the northern part of the country, and separatists in the south. But with local officials acknowledging that al Qaeda is now stronger than ever, Yemeni forces are gearing up for more intense fighting around the country.

VIDEO: The president returns from vacation to confront mounting security concerns.Play

"Their idea is to overtake whole of Yemen," Yemen Army Gen. Yahya M.A. Saleh told ABC News. "Al Houthi wants part of Yemen, separatist groups want part of Yemen, al Qaeda wants the whole Yemen, not only to stay in Yemen, but to spread all over the world and export terrorists."

Additional U.S. special forces have been deployed to Yemen to help the local army and security forces with counterterrorism training, and to provide intelligence and firepower.

"Instability in Yemen is a threat to regional stability and even global stability," Clinton today said at a joint press conference with Hamad Bin Jassim Jabr Al-Thani, Prime Minster and Foreign Minister of Qatar. "This is a difficult set of challenges but they have to be addressed."

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Training and providing assistance to locals will be the key to fighting the war against terrorism but Americans shouldn't expect U.S. military action in Yemen, Washington Post reporter Bob Woodward said today,

"It's confusing, I think, to the average person," he said on "Good Morning America. "We've got these ground wars in Iraq and Afghanistan, but al Qaeda sanctuaries are in Pakistan, in places like Yemen, we don't have ground wars going on.

VIDEO: TSA puts extra layers of security in place following Christmas bombing attempt. Play

"The president there has taken a very aggressive stance in going after al Qaeda -- the key to this ground operations by other countries, quite frankly," Woodward told "GMA's" George Stephanopoulos.

And it is not only in Pakistan and Yemen where alleged terror groups are breeding.

"Somalia ... is another place of worry," Woodward said. "In fact, there are dozens of places of worry where there are al Qaeda cells around the world."

Obama, who cut his vacation short, plans to hold an inter-agency meeting Tuesday to discuss missed intelligence signals and security failures in the case of the 23-year-old Nigerian national who attempted to blow up a U.S.-bound airplane on Christmas day. Yemen and future security measures are also likely to be the subjects of discussion.

Christmas Day Terror Plot

Officials, both in the United States and in Yemen, are trying to dig deep into the botched Christmas Day terror plot, where Umar Farouk Abdulmutallab, 23, tried to blow up a Detroit-bound plane with the explosive PETN strapped to his underwear.

In Yemen, officials are hoping to trace the steps of the Nigerian national who studied at an Arabic language institute there months ago. A student there told ABC News that while he was religious, Abdulmutallab never struck him as an extremist.

"He definitely believed with all his heart in religion but there was nothing extreme, there was nothing fundamental about it," Canadian student Matthew Salmon said.

But officials say as soon as Abdulmutallab left the language school, he met up with al Qaeda operatives who gave him training and the bomb with which he tried to blow up Northwest Flight 253 on Christmas day. It is that kind of training, officials fear, that other suicide bombers preparing for attacks have received.

The Obama administration has issued new security directives to combat threats of terrorist attack. Starting today, passengers coming to the United States from Afghanistan, Algeria, Iraq, Lebanon, Libya, Nigeria, Pakistan, Saudi Arabia, Somalia, or Yemen, or designated as a state sponsor of terrorism, Cuba, Iran, Sudan, and Syria, will be subject to enhanced screening.

"TSA is mandating that every individual flying into the U.S. from anywhere in the world traveling from or through nations that are state sponsors of terrorism or other countries of interest will be required to go through enhanced screening," a statement from the agency read. "The directive also increases the use of enhanced screening technologies and mandates threat-based and random screening for passengers on U.S. bound international flights."

Obama's top counterterrorism adviser, John Brennan, took to the airwaves Sunday to acknowledge the system failed in connecting the dots in the case of Abdulmutallab, but he also insisted that no obvious plot was missed.

"There was no single piece of intelligence, a smoking gun, if you will, that said that Mr. Abdulmutallab was going to carry out his attack against that aircraft. What we had, looking back at it now, were a number of streams of information," Brennan said on "This Week" Sunday.

"We may have had a partial name, we might have had an indication of a Nigerian, but there was nothing that brought it all together."

Today, Clinton also acknowledged the failure of connecting the dots in the case of Abdulmutallab, but also defended the State Department's actions. The U.S. embassy in Nigeria sent a memo to various agencies after the terror suspect's father approached Americans with concerns that his son may be getting increasingly radicalized.

"We are not satisfied. We are conducting an internal review," Clinton told reporters. "Based on what we know now, the State Department fully complied with the requirements set forth."

Republicans were less charitable with their criticism.

"There are probably a number of people who screwed up," GOP Sen. Christopher Bond of Missouri said on "Fox News Sunday."

"We may need more I.T., better information systems. But with ... all of the leads dangling out there, somebody screwed up on not reporting it."

Former Vice President Dick Cheney and others have accused the Obama administration of not taking the fight against terrorism seriously enough.

Woodward said the administration, which is coming up on its first full year, has probably done more than its predecessors to address the growing threat of al Qaeda.

"You can't become president a year ago, as he did, and not realize we're at war. It's part of the fabric of life there, of the decisions of the intelligence briefings," Woodward said. "The information that I have about that it's very clear that the new administration has taken a very aggressive stance on these matters and are perhaps -- even more than the Bush administration -- doing more about the al Qaeda sanctuaries in places like Yemen, and again this is the key."

But, Woodward said, U.S. agencies should've at least checked if Abdulmutallab had a U.S. visa after they received intelligence from his father in Nigeria that he was being radicalized, and put him on the "no-fly" list. And security, Woodward said, should be focused on airlines but the threat could be everywhere.

"All the focus on airline security, obviously, it's a big deal but al Qaeda has capabilities to do other things -- how about trains, how about buses," Woodward said. "The administration has to worry about being like the generals fighting the last war, you can't fight the last terrorist attack it could come anywhere, any place."

White House Pushes Back

White House Officials have aggressively pushed back against criticism that the administration is not focused on al Qaeda, pointing to how much more attention and resources they have sent to places such as Yemen, Pakistan and Afghanistan than the prior administration.

"Throughout this year, the president has urged greater focus on and investment in the fight against al Qaeda in the Arabian Peninsula and on support for the government of Yemen and other regional partners' efforts against those extremists," a senior administration official said.

"To keep the pressure on al Qaeda Central in Pakistan, we have also increased the pressure on its affiliates in Yemen, Somalia, and elsewhere. That is why the president dispatched his counter terrorism advisor and the Commander of CENTCOM to Yemen earlier this year, and it is why we are increasing our investments in and training of Yemeni forces to counter al Qaeda and its murderous agenda.

"These efforts have already yielded important successes in disrupting al Qaeda efforts and plotting in Yemen. Our actions have made clear that we are determined to seek out and destroy al Qaeda wherever it might hide."

U.S. officials met with Saudi and Yemeni authorities this past weekend to discuss the threat of al Qaeda and the separatist movements in the country.

Even U.S. Gen. David Petraeus visited Yemen this weekend to meet President Ali Abdullah Saleh to thank him for his efforts in fighting terrorism and pledge further U.S. support. The senior army general also visited U.S. special operations teams that are helping train Yemenis in counterterrorism.

ABC News' Richard Coolidge and Jake Tapper contributed to this report.