A suicide bomber has struck at a bus in northern Israel with a car packed with explosives, killing himself and at least 18 others, and injuring many more.
Several hours after the bombing, Israeli tanks backed by Apache attack helicopters rolled into the West Bank town of Jenin, just a few kilometres away.

The suicide bomber attacked the bus at Megiddo junction, near the biblical city of Armageddon (now Megiddo) and close to the West Bank, during the morning rush hour, detonating explosives as he pulled up behind it in his car.

It was the biggest suicide attack since Israel's West Bank offensive, with most of the casualties Israeli soldiers.

As the tanks entered Jenin, which Israel regards as a key base for Palestinian militants, the helicopters opened fire with machine-guns.

Yasser Arafat's Palestinian Authority condemned the attack and denied any involvement.

Prime Minister Ariel Sharon held a scheduled cabinet for three hours on Wednesday but no decision was announced in relation to the Megiddo attack.

An official statement by Mr Arafat's administration said: "The Palestinian leadership condemns the attack near Megiddo and stresses this has nothing to do with the Palestinian Authority or its security services."

US envoy William Burns, on a visit to Lebanon, said that all parties to the conflict had to "show commitment for the political path".

The Israeli authorities said they were checking reports that a 19th body found at the scene was that of the suicide bomber.

A Palestinian militant group, Islamic Jihad, claimed responsibility for the attack, saying it was timed to coincide with the 35th anniversary of the 1967 Six-Day War, when Israel captured the West Bank and Gaza Strip.

"A seeker of martyrdom... from the Jerusalem Brigades detonated an explosives-laden car that he drove near a Zionist bus near Megiddo junction," it said.

The group did not give the attacker's name, saying it feared reprisals against his family, but promised to release it eventually.

Eyewitnesses said some passengers on the bus, which was travelling from Tel Aviv to the town of Tiberius, were trapped by flames as it continued to burn long after the blast.

The vehicle was reduced to a scorched metal skeleton.

One young soldier, Sharon Levinger, managed to escape from the bus as he was sitting at the front.

The blast, which came at 0715 local time at the height of the rush hour, turned the bus over twice, he said.

The initial explosion appears to have been succeeded by a second when the fuel tanks of the bus blew up.

Ogen Drori, a paramedic, witnessed the "huge" explosion from a nearby car.

"The people were thrown out of the bus by the force of the bomb," he said, adding that the heat meant rescuers could not board the vehicle.

He confirmed that many of the casualties were soldiers.

The explosion scattered body parts and personal effects across the street and a number of the dead bodies were wearing the familiar olive-green uniform of the Israeli army.

Israeli Government spokesman Avi Pazner accused Mr Arafat's Palestinian Authority of "doing everything to encourage terrorist organisations to continue their attacks".

Palestinian militants have carried out more than 60 suicide attacks since the current uprising began in September 2000.

The latest attack came after Mr Sharon approved the construction of a 110-km barrier designed to separate the West Bank towns Jenin, Tulkarm and Qalqilya from Israeli cities.

Some recent suicide bombings have been carried out by Palestinians from these towns.