The Israeli army is tightening its siege of Palestinian leader Yasser Arafat's compound in the West Bank town of Ramallah, as the number killed by Thursday's suicide attack in Tel Aviv rose to six.

Israeli forces have already arrested some people in the compound

Tanks are surrounding the compound, and two big explosions have been heard. Witnesses report seeing clouds of smoke rising from the area.

Palestinian sources say the Israelis have been blowing up some of the few buildings still standing in the compound.

One of those demolished is thought to be directly behind the building where Arafat is currently located.

There has been no immediate comment from the Israeli military. Soldiers are patrolling the streets, making it difficult for anyone to get near the Palestinian leader's office.

	Arafat's Ramallah compound Known as the Muqataa Built by the British in the 1920s Palestinians took control in 1994 year after Oslo peace accords See also: Description of Yasser Arafat's Ramallah compound

During the night, about 20 Palestinians wanted by the Israelis left the compound and surrendered.

However, the army is demanding the surrender of other key figures it believes are inside.

The BBC's Orla Guerin in Jerusalem says Israeli sources are talking about an unlimited stay.

Palestinian spokesman Nabil Abu Rudeinah told the BBC that Mr Arafat's life was in real danger and said it was very possible that Israel would exile him to the Gaza Strip or abroad.

Mr Abu Rudeinah said Mr Arafat was in touch by phone with Arab and European leaders, seeking meetings of the United Nations Security Council, Arab League foreign ministers and the so-called Middle East quartet of the United States, the European Union, Russia and the UN.

Helicopter fire

The siege coincided with two Israeli army incursions into the Gaza Strip, with one group advancing to the edge of Gaza City and another penetrating two kilometres (one mile) near the towns of Beit Lahiya and Beit Hanun.

Witnesses in Gaza City saw tanks and helicopters fire into the densely populated Shijaia district.

Two Palestinians - a man and a woman - were killed by the Israeli fire. Witnesses said that troops blew up several metal workshops in Gaza.

Military sources said three soldiers were wounded when their tank drove over an explosive device.

Thursday's bombing was the second in two days - the first fatal suicide attacks in Israel for six weeks, although violence had continued in the West Bank and Gaza Strip.

A Palestinian bomber blew himself up on board a crowded bus in Allenby street, instantly killing five people and injuring about 50 others.

One of those who was critically wounded - a young man from Scotland - has since died of his injuries.

'Cruel terrorism'

Israel's Cabinet met for a full emergency session for the first time in six months on Thursday night and decided to "isolate" Mr Arafat.

But the question of expelling the Palestinian leader was apparently dropped on the grounds that it would do Israel more harm than good.

The tanks are reported to have fired on the buildings

"Israel is engaged in a long and hard battle against a cruel and abject terrorism led by Palestinian Authority chairman Yasser Arafat who has set up a terrorist coalition," said a statement from Israeli Prime Minister Ariel Sharon's office.

"Israel knows how to face and continue this battle with firmness and it will triumph," it added.

The wanted Palestinians inside Mr Arafat's compound are accused of mounting attacks on Israelis.

They include the head of West Bank intelligence, Tawfiq Tirawi, accused by Israel of involvement in terrorist activities, and Mahmud Damra, the leader of Mr Arafat's Force 17 bodyguard.

Palestinians said the Israeli tanks had opened fire on Mr Arafat's headquarters, wounding two of his security guards.

Mr Arafat himself is reported to be unharmed.

But Israeli army officials said their troops only fired when fired upon by Palestinian gunmen.

Israel accuses the Palestinian leader of not doing enough to stop suicide bombings.

It has kept him confined in Ramallah for almost a year, destroying most of his compound, and decimating his security forces.