Israeli forces have moved into the West Bank town of Jenin in apparent retaliation for a suicide bomb attack in Israel which killed 17 people, including the attacker.

The detonation of a moving car packed with explosives alongside a bus in the morning rush hour marked a new and more deadly approach by suicide bombers which was immediately condemned by the US.

In [President Bush's] eyes, Yasser Arafat has never played a role of someone who can be trusted and who is effective

White House spokesman Ari Fleischer

The attack was also denounced by the Palestinian Authority, which for the first time said it had no prior knowledge of it.

But a White House statement called on the entire Palestinian leadership - not just its chairman Yasser Arafat - to do more to stop the attacks.

The morning bombing which killed 13 soldiers and three civilians was claimed by the radical Islamic Jihad group, which said the dead bomber came from Jenin.

'War retaliation'

The group said the attack was timed to coincide with the 35th anniversary of the 1967 Six-Day War, when Israel captured the West Bank and Gaza Strip.

About 30 tanks plus troops backed by helicopter gunships headed for the centre of Jenin, only 15 kilometres (10 miles) from the scene of the suicide attack at Megiddo, the Hebrew name for the Biblical town of Armageddon where good battled evil.

The army described the action as a "routine patrol".

Jenin was placed under military curfew overnight.

Israeli Prime Minister Ariel Sharon delayed by one day his visit to Washington to hold more talks on the Middle East situation with President Bush.

Mr Sharon's government blamed Mr Arafat for the bus attack and Mr Bush's spokesman Ari Fleischer said: "In the president's eyes, Yasser Arafat has never played a role of someone who can be trusted and who is effective."

US seeks new leadership

A senior Bush administration official briefed American reporters under condition of anonymity that US leaders were actively seeking someone else who could lead the Palestinians towards peace with Israel.

The White House spokesman was more circumspect on this point, but Mr Fleischer did say Mr Bush was "less focused on any one individual, and more focused on actions and results".

"What the president is interested in is results, from whatever corner they may come," he said.

"If that's Chairman Arafat, that's fine with the president. If it's others, that's fine with the president."

Passengers trapped

Witnesses to the morning attack said some passengers were trapped as flames engulfed the bus, which was travelling from Tel Aviv to the town of Tiberias.

The bus was hurled across the road by the force of the blast

The vehicle was reduced to a scorched metal skeleton.

The blast from the exploding car, which came at 0715 local time (0415GMT) at the height of the rush hour, was so strong it turned the bus over twice.

Ogen Drori, a paramedic who witnessed the explosion said people "were thrown out of the bus by the force of the bomb".

The BBC's Jeremy Cooke in Jerusalem said the use of a moving car bomb against a bus was a new kind of attack for Palestinian militants, who had previously used people equipped with belts of explosives.