An explosion rocked Moscow's busiest airport today in an apparent "terrorist attack", killing 35 and injuring dozens more, according to Russian officials.
The blast erupted in the arrivals area of the Domodedovo airport at 4:40 p.m. Moscow time. In addition to the 35 dead, another 130 were injured in what investigators called a suicide bombing.
Evgeny Khorishko of the Russian Embassy in Washington, D.C., told ABC News it was "too early to say" who may have been responsible.
"As you know there was an explosion in Domodedovo. Preliminary version is that it was a terrorist attack," Russian President Dmitry Medvedev told reporters. "People were killed and injured in that blast. I have just talked to the Healthcare Ministry and Emergency Ministry... We need to do all we can to make sure that victims get immediate medical help. Many ambulances are headed for Domodedovo and I would like to express my condolences to relatives of the victims."
Initial reports published earlier today by Russia's state news agency RIA said witnesses had seen two suicide bombers carry out the attack. Later reports pointed to a single attacker. On Twitter, one purported eyewitness, Ilya Likhtenfeld, said the bomb was on a man standing in a crowd near a cafe.
U.S. President Barack Obama said he "strongly condemns this outrageous act of terrorism against the Russian people" and offered his condolences to those affected, according to a statement read today by White House press secretary Robert Gibbs. The U.S. State Department said it has no indication that any Americans were among those killed or injured.
Video taken inside the airport apparently minutes after the bombing shows the blast area full of smoke, with luggage scattered around the ground. Several bodies, prone and unmoving on the ground, are also visible.
Emergency services are on the scene and have evacuated several people from the blast zone, witnesses said according to The Moscow Times.
"All the injured r taken away. The bodies r not taken away," Likhtenfeld said on Twitter. "The investigation is going on. They r looking for the remnants of the suicide bomber."
Medvedev said a special investigative committee would be established to look into the incident and is currently meeting with law enforcement and the mayor of Moscow in response to the explosion, Khorishko said.
Security Measures Added Before Checkpoints in U.S., TSA Says
In response to the attack, passengers traveling through airports in the U.S. may see "unpredictable" security measures today, the Transportation Security Administration said, including some checks before travelers reach the usual security checkpoints.
"We are monitoring the tragedy at Moscow's Domodedovo airport. As always, we are working with our international partners to share information regarding the latest terrorist tactics and security best practices," the TSA said in a statement just hours after reports of the Moscow bombing emerged. "Passengers may continue to notice unpredictable security measures in all areas of U.S. airports, including before the checkpoint. These measures include explosive detection technology, canine teams and Visible Intermodal Prevention and Response (VIPR) teams, among other measures both seen and unseen."
Bombing Latest in Russia's Bloody History of Attacks
No hard evidence has emerged yet to link the Domodedovo bombing to any specific terrorist group. However, according to former White House counter-terrorism adviser and ABC News consultant Richard Clarke, it fits the pattern of a persistent Chechen campaign of violence.
"This is part of a pattern where the Chechen rebel group attacks in Moscow or in Russia – a major attack about every two years," Clarke said. "They've attacked in the metro, they've attacked in schools, they've attacked in apartment buildings… This is a regular pattern."
Suicide bombers, often female, from Chechnya or Dagestan and sometimes known as "black widows," have carried out many attacks on Russian targets in the past decade, including the simultaneous bombings of two planes mid-flight that killed 90 people in the summer of 2004 and a Moscow metro bombing that killed 10 a week later.
"Black widows" are often avenging the deaths of relatives at the hand of federal forces.
Last March, two female suicide bombers attacked the Moscow subway, killing 40 people and injuring more than 100.
Both women were from Dagestan in the restive North Caucasus region where Russian forces have been battling an Islamist insurgency. One was a 28-year-old schoolteacher, the other the 17-year-old widow of a local militant leader who was killed by Russian forces in 2009.
A Chechen militant leader, Doku Umarov, claimed he ordered the metro attack and warned of more attacks to come in a video posted online.
"Both of these operations were carried out on my command and will not be the last," Umarov said.
On Jan. 21, three days before the Domodedovo bombing, Russia's prime minister, Vladimir Putin said Russia must combat terrorism in the North Caucases by improving the quality of life for the people there.
"Our objective is to radically change the situation in the North Caucasus, primarily by improving the quality of life of the people, ensuring their security and giving them the opportunity to work and live in peace," Putin said. "We must eradicate the roots of terrorism and extremism, first of all poverty, unemployment, ignorance and inadequate levels of education, and corruption and lawlessness."
ABC News' Max Karmen and Dragana Jovanic contributed to this report.