Baghdad: Protesters burned Israeli and American flags on Sunday in a string of Arab countries and demanded a stronger response from their leaders to Israel's attack on Gaza.

"Arab silence is behind the bombings," read a banner held by one of several thousand people who turned out in the Sunni Arab city of Samarra north of Baghdad.

The Israeli raids incensed many in the Arab world, where many governments are seen by popular Islamist movements as collaborators with the United States or Israel.

"America and the Zionists are the leaders of world terrorism," read a placard held by protesters at the UN headquarters in the Lebanese capital Beirut. They demanded UN intervention to end the Israeli onslaught.

Similar protests were held in Palestinian refugee camps in Lebanon, home to some 400,000 refugees displaced when Israel was established in 1948.

In the centre of the Syrian capital Damascus, thousands of people carrying Palestinian and Syrian flags filled streets around a popular square, chanted anti-US and anti-Israeli slogans and burned an American flag.

"Victory belongs to heroic Gaza," one banner said. "Until when will the Arab silence continue?" read another.

In Baladiyat, a Baghdad district inhabited by many Palestinians given refuge in Iraq under Saddam Hussein, men waved banners and condemned Arab nations for not doing enough to support Palestinians.

"We have been waiting for action from Arab leaders for almost 60 years," Jaleel Al Qasus, the Palestinian envoy to Iraq, said during the protest by several hundred people.

"Our efforts have been in vain."

Scores of protesters tried to approach the Egyptian embassy in Beirut to demand Egypt open up its borders to Gaza. Police used tear gas to stop the demonstrators approaching.

In Egypt itself, protesters gathered in Cairo and five other towns, security sources said. They burned Israeli flags and carried placards denouncing Israel.

The office of Grand Ayatollah Ali Al -Sistani, the reclusive cleric who has peerless influence among Shi'ites in Iraq, issued a statement condemning what he called a 'savage' operation.

"The Arab and Muslim world demand, more than ever, a practical stance to stop this never-ending offensive," it said.

Iran's Supreme Leader issued a religious decree ordering Muslims around the world to defend Palestinians in Gaza against Israeli attacks "in any way possible". "Whoever is killed in this legitimate defence, is considered a martyr," he said.

Several protests were held in the capital Tehran, including one by Iranian lawmakers chanting "Death to Israel".

In Yemen, the ruling party of President Ali Abdullah Saleh organised a demonstration attended mainly by civil servants who agreed at a stadium in the capital Sanaa to send a ship with humanitarian aid to Gaza.

"Israel is your enemy; unify your ranks Arabs," read a banner and protesters chanted: "Gaza, your blood is our blood!"