"No to the occupation! No to America!" chanted the demonstrators, who had gathered in Tahrir Square after Shia leader Moqtada Sadr called for a demonstration "in support of Gaza" and against Israel, an AFP journalist reported.

Protesters waved Palestinian and Iraqi flags while a huge Israeli flag was laid on the ground for the demonstrators to trample on.

"This rally is aimed at condemning what is happening in occupied Palestine, the bloodletting and the violation of rights," said Abu Kayan, an organiser of the protest.

Moqtada Sadr's movement has imposed strict security measures around Tahrir Square, while Iraqi security forces are deployed in large numbers around the rally site.

The firebrand Shia cleric wields great political influence but is not part of the government.

But the movement of support for Gaza is backed by the Iraqi government, which defends the Palestinian cause.

Israel is carrying out a brutal war against Hamas, after the Gaza-based militants stormed its southern border at the weekend, killing more than 1,200 Israelis.

Israel has since carried out a grisly retaliation, bombarding the Gaza Strip with round-the-clock air strikes while imposing a complete siege on the Palestinian enclave that has stopped water, food and electricity from reaching about 2.3 million Palestinians.

So far, some 1,537 Palestinians have been killed by the Israeli army. Children and senior citizens account for 60 percent of casualties, Palestinian health ministry figures say.

On Friday, the Israeli army called on Gazan Palestinians to evacuate their homes in 24 hours and head south of blockaded territory ahead of an anticipated ground invasion. It was not immediately clear how many people were currently located north of Wadi Gaza.

“This evacuation is for your own safety,” the Israeli military said, in a warning it said was sent to Gaza City civilians. 

Hamas, in a statement, said "our Palestinian people" rejected Israel's Gaza evacuation order.

Carrying plastic bags of belongings, with suitcases on their shoulders and children in their arms, Gazans were, however, moving to safer areas on Friday.

More than 423,000 people have already fled their homes in the territory, according to the UN.

Such an evacuation order could transform "what is already a tragedy into a calamitous situation," a UN spokesman said.

The UN Relief and Works Agency for Palestine Refugees (UNRWA) later said it had moved its central operations centre and international staff to the south of Gaza.

A Security Council meeting on the conflict has been called for Friday.

*This story was edited by Ahram Online