US brands Arafat 'ineffective' after massive car bomb
Israeli tanks have rolled into Jenin, just hours after Islamic militants blew up an Israeli bus, killing 18 people and wounding at least 40.
An Israeli security officer walks by the remains of the passenger bus destroyed by the huge bomb blast at a busy road junction near the ruins of Megiddo
Mr Yasser Arafat's Palestinian Authority denounced the bombing and, in a move that seemed designed to forestall retaliation, said its security services had launched a hunt for militants.
The attack on the bus prompted condemnation from US President George W. Bush, whose spokesman called Arafat "ineffective" and a leader who could not be trusted.
Israeli Prime Minister Ariel Sharon put off by a day a planned visit to Washington in order to consider a response.
The Israeli security cabinet met in a session planned before the attack. It announced no decisions, but is expected to launch what could be a harsh military response.
The blast took place at Megiddo, the biblical Armageddon, between the Israeli port city of Haifa and the Palestinian West Bank town of Jenin.
Police said the blast was caused by explosives packed into a car which overtook the packed bus as it plied the route between Tel Aviv and Tiberias.
The attack was the fifth by Palestinians in the last month.