GAZA CITY, September 28 (IslamOnline & News Agencies) - More than 20,000 Palestinians marched through Gaza City to mark the second anniversary of the Intifada Saturday as Palestinian President Yasser Arafat urged the crowd from his besieged West Bank headquarters to press on with a third year of uprising.

The Palestinian leader, who has been trapped in his battle-scarred Ramallah office for nine days, spoke to the crowd on his mobile phone, urging them to continue their struggle against Israeli occupation despite the 2,500 lives it has already claimed.

"I am speaking as I am under siege. But we don't care about the siege or any other conspiracy against us. We will be victorious," he said in speech relayed through loud speakers to demonstrators as they marched from the central Palestine Square to parliament.

"We want to defend our holy places, both Christian and Muslim, to defend occupied Jerusalem and every centimeter of our land. Our resolution will continue and we will be the winner, the victory will be ours," Arafat repeated.

"They [the Israelis] are now trying to hurt us with all their force and weapons but I tell them, no one can break the will of the Palestinian people, and the will of the Palestinian people is occupied Jerusalem as the capital of a Palestinian state," he said.

Among the sea of Palestinian flags held aloft by demonstrators, many also waved his trademark keffiyah -- or Palestinian headdress -- and posters of their beleaguered leader, as they chanted: "We will support our president from siege to siege."

Top Palestinian negotiator Saeb Erakat even told an Egyptian newspaper published Saturday Israeli Premier Ariel Sharon could soon kill Arafat.

"Sharon wants to undermine Arafat and could kill him soon because [Arafat] insists on an Israeli withdrawal to the borders of 1967, and the creation of a Palestinian state with Jerusalem as its capital," he said.

But Arafat has shown no sign of backing down and, following a series of rare rebukes by its chief U.S. ally over deadly military operations, Israel was coming under increasing pressure to end the crisis.

According to political sources, Sharon dispatched his chief of staff Dov Weisglass to Washington to hold a meeting with U.S. National Security Adviser Condoleezza Rice on means of ending the Ramallah siege.

Arafat's mainstream Fatah movement issued a statement Saturday, calling on the Palestinian people to continue its uprising. "This nation knows only one language: self-defense and no surrender."

Palestinian resistance groups maintained a large presence in demonstrations around the Gaza Strip which merged in the main rally in Gaza City.

The colors of Islamic Jihad and Hamas were much in evidence, while the Al-Aqsa Martyrs Brigades, an armed offshoot of Arafat's Fatah, promised the crowd through loudspeakers to step up its attacks against Israel.

Hamas spiritual leader Sheikh Ahmad Yassin was present at the demonstration and added his voice to the calls for a third year of uprising, including resistance attacks.

"The Palestinians will continue the Intifada against the Zionist entity in their tanks, their helicopters and their bulldozers," he told AFP.

"The martyrdom operations and the mortar attacks will continue and will escalate because these are the only weapons we have and this enemy understands only the language of force."

For his part, senior Islamic Jihad leader Mohammed al-Hindi said the persistence of the uprising in the face of the high casualty toll gave the lie to Israeli boasts that there could be a military solution.

"The Intifada is proof that after two years, they cannot control the Palestinian people by force," Hindi told AFP.

"The struggle is proof the Zionist entity is trying to make false history which is not true."

Ahead of the main rally in Gaza City, hundreds of youths took part in marches in towns and refugee camps across the Gaza Strip, some of which were followed by clashes with the Israeli army.

A teenager was killed when Israeli soldiers opened fire on stone-throwing demonstrators near the Jewish settlement of Netzarim, Palestinian security sources said.

Two more Palestinians were injured in the same incident, while similar clashes wounded six youths near Beit Lahia and one in Khan Yunis, Palestinian medical and security sources said.

Earlier a local leader of the Al-Aqsa Martyrs Brigades, was shot dead in his home in the southern Gaza Strip as Israeli troops fired on buildings in the area, witnesses said.

The anniversary demonstrations, which began on Friday and were expected to continue into Sunday, came against a backdrop of heightened tension amid revenge calls from Hamas for a failed Israeli assassination bid against their Gaza military leader Mohammad Deif which killed two other Palestinian resistance fighters.

Security forces in Israel were on high alert following the abortive missile strike Thursday.

Fear of reprisals for the attack on Deif, top of Israel's wanted list, put the Israeli occupation army on even higher alert.

"There is an increased awareness among troops ... because it is the two year anniversary of the Intifada, and because of the attempt on Mohamed Deif's life and the reaction to that," an Israeli army spokeswoman said.

Extra security forces were deployed in Israel's main cities, in malls and bus stations, while checkpoints along the Green Line separating Israel from the West Bank were beefed up.

Palestinians were urged to protest against the Israeli occupation by staging a mass rally and opening shops and offices in defiance of the Israeli occupation army's curfew Saturday.

State schools were open and small numbers of pupils could be seen on the streets but most shops were closed.