Israelis Mount Assault on Arafat Complex

Israeli military forces once again pushed into the West Bank city of Ramallah and mounted an armed assault on Yasser Arafat's headquarters, according to media reports.

The Israeli action early Thursday took place less than 24 hours after a car bombing in northern Israel that killed 17 passengers on a bus. Palestinian militants claimed responsibility, although two different groups said each was responsible.

Israeli military sources confirmed an action was taking place inside Ramallah but declined to discuss details, according to Reuters. In Jerusalem, which is south of Ramallah, muffled booms could be heard.

Palestinian sources said the Israeli tanks were firing heavy machine guns at the complex of Arafat, the Palestinian leader who is viewed as an enemy by the government of Israeli Prime Minister Ariel Sharon.

Witnesses told The Associated Press at least two tanks and three armored personnel carriers have surrounded Arafat's office compound.

Rush-Hour Tragedy

The car bomb was detonated alongside a crowded bus near the Israeli city of Megiddo, a few miles from the northern border of the West Bank, during the Wednesday morning rush hour.

The explosion ignited the fuel tank of the bus, and the force of the ensuing blast threw some passengers from the vehicle and trapped others in an inferno that left the bus a mangled wreck of molten metal.

Hours after the blast, Israeli forces attacked the West Bank city of Jenin, according to Palestinian security sources. Helicopters fired machine guns into the city and a nearby refugee camp that came under heavy Israeli attack earlier this year. Tanks and troops had also moved into the city, Palestinian sources said.

Jenin is now under Israeli military curfew. However, Israeli officials said there were routine operations.

The Islamic Jihad claimed responsibility, saying the attack marked the 35th anniversary of the 1967 Mideast War, during which Israel occupied the West Bank and Gaza Strip. The bomber is widely believed to have come from the refugee camp near Jenin and residents of the shattered camp were preparing for an Israeli retaliation.

However, the Al Aqsa Brigades — which has been linked to Arafat's Fatah movement — also claimed responsibility.

But Arafat's Palestinian Authority issued a statement condemning the attack and said it had no advance knowledge or any ties to the bombing. Sources in the Palestinian Authority told Reuters that if it was proven that Islamic Jihad was responsible for the attack, members of the militant group would be rounded up and arrested.

Death, Destruction and Tears

The Megiddo junction was a scene of utter panic and destruction. Survivors said they saw passengers trapped in the fire that consumed the bus, while the bodies of several others were hurled through the air by the impact of the blast.

"I felt the bus leap and then turn over," driver Mickey Harel, who has survived three previous attacks in the past seven months, told The Associated Press today. "I saw soldiers thrown around the front of the bus."

Most of the victims are believed to have been Israeli soldiers. The bus was traveling from Tel Aviv to the town of Tiberius.

In a particularly harrowing story, Israeli Army Radio reported that a couple hugged each other as they burned to death.

"A car drove alongside the bus and exploded. The bus burst into flames, and it's a tough sight; the bus is completely burned out," regional police Chief Yaakov Borovsky told army radio.

"It is one of the worst attacks we have sustained [in the last 20 months] from the standpoint of casualties," Shlomo Aharonisky, the national police chief, told reporters.

Officials believe the level of damage suggests a powerful new type of car bomb is being used. Witnesses say debris and human remains were scattered for hundreds of yards down the highway.

Israeli Intelligence Says 'Mega-Attack' Planned

The use of a moving car bomb against a bus is widely believed to be a new form of suicide attack by Palestinian militants, who have earlier tended to use explosive belts strapped onto the waists of suicide bombers. In recent months, a few female suicide bombers have carried explosives in backpacks, presumably due to the weight and bulk of the belts.

Israeli military officials said Palestinian militants were trying to carry out another "mega-attack," like the March 27 bombing of a Passover Seder in the Israeli coastal town of Netanya.

Israeli army spokesman Brig. Gen. Ron Kitrey told reporters today that Maj. Gen. Aharon Zeevi, the Israeli military chief of intelligence, had told a parliamentary committee that militants had attempted to use cyanide gas in the Passover attack. However, Israeli experts believe the gas was not released to due a technical difficulty.

The bombing at the Park Hotel in Netanya killed 29 people and triggered Operation Defensive Shield, the Israeli military offensive in the West Bank earlier this year.

Meanwhile, White House spokesman Ari Fleischer condemned today's attack. "These terrorists are the worst enemies, not only of the people of Israel who seek peace, but also of the Palestinian people and their hopes for a better life," said Fleischer.

Today's attack underlined the importance of reforming the Palestinian Authority's security apparatus, Fleischer added.

CIA Director George Tenet is currently in the region to discuss the issue with Palestinian and Israeli officials. On Tuesday, Tenet met with Arafat to press the Palestinian leader to carry out reforms in the Palestinian Authority's bloated security system.

President Bush is expected to meet with Sharon in Washington next week. Amid reports that a Middle East peace conference was being planned in Turkey next month, Bush will also meet with Egyptian President Hosni Mubarak later this week.

ABCNEWS' Gillian Findlay in Jerusalem contributed to this report.