Widespread protests erupted today throughout the Arab world in a second day of demonstrations against the U.S.-led war in Iraq. Violence claimed three lives in Yemen, including a policeman and an 11-year-old boy killed in a melee outside the U.S. Embassy.

The deadly violence in Sanaa, the Yemeni capital, occurred when bullets, rocks and tear gas were used during a confrontation between police and 30,000 protesters, who shouted "Death to America!" Three people were in critical condition and dozens were injured, according to Yemeni news reports.

There were also violent clashes during protests at the fabled 1,000-year-old al-Azhar mosque in Cairo, the Egyptian capital and the largest city in the Arab world.

The chaos began after Friday prayers turned into a rancorous antiwar protest when more than 20,000 people squeezed into the courtyard of the mosque. Worshipers threw shoes and stones at riot police, who beat hundreds of protesters with large sticks as the surging crowd attempted to move the rally to the streets.

Elsewhere, hundreds of protesters marched in Bahrain, where the U.S. Navy's 5th Fleet is based. "Arab leaders unify. Support Iraq," the protesters chanted, and police periodically fired rubber bullets.

In Jordan, after thousands of protesters clashed with baton-wielding riot police in Amman, the capital, King Abdullah told his countrymen to remain calm.

While the protests focused anger on the United States, there also was criticism of the role Arab leaders have played in the Iraqi war.

"The Arab leaders will be held responsible for any child who is killed in Iraq," read an editorial issued by Jamahiriya, Libya's official news agency.

Demonstrators in Syria attacked the Egyptian Embassy, calling President Hosni Mubarak of Egypt "an American agent."

The demonstrations underscored the dilemma faced by Arab leaders in managing the outrage among their citizens, especially in countries such as Saudi Arabia and Jordan, which have allowed U.S. troops to establish bases on their soil. Egypt, a longtime U.S. ally and aid recipient, has quietly granted the United States overflight rights for combat aircraft.

A prominent political analyst in Cairo said that if protests grew more violent, Arab leaders would face "a serious threat."

"Arab leaders, especially in Egypt and in the Persian Gulf, are in a very, very, very dangerous situation. We could all feel this danger coming," said Diaa Rashwan, head of the comparative politics unit at the Al-Ahram Center for Political and Strategic Studies in Cairo. "They are against a wall and between two fires, their internal pressures and their friendships with the United States."

With the violent protests in Yemen, where gun ownership and lawlessness are widespread , there was increased concern about the presence of Islamic militants. Even though the Yemeni government opposes the war in Iraq, leaders there are trying to manage the chaos, fearful that passion in the streets could turn against them. Since the Sept. 11, 2001, terrorist attacks on the United States, the government said it has been trying to arrest those with suspected ties to Osama bin Laden's al Qaeda network.

The protests in Yemen turned violent when protesters marched several miles from a mosque to the U.S. Embassy, throwing stones and hurling tear gas canisters back at police. They chanted, "No American and no British Embassy on Yemeni land!" and, "Death to Israel!" Police unleashed a barrage of bullets, fired water cannons and began firing automatic rifles into the air.

In Egypt, Friday prayer services were punctuated with leaders giving passionate anti-American sermons and cries of support for the Iraqi people.

At Cairo's al-Azhar mosque, Sheik Mohammed Sayed Tantawi, recognized by many as the paramount scholar in Sunni Islam, called for jihad, or holy war. But he focused on support for the Iraqi people. He did not mention the United States or Iraq's president, Saddam Hussein.

"Jihad in Islam is meant to defend the religion, money, soul and freedom and to support those who were subject to injustice," he said. "Islam supports defending the righteous path, and we have to support and defend the people of Iraq."

After his sermon, thousands of people, some carrying children on their shoulders, others holding up copies of the Koran, the Islamic holy book, attempted to march to Tahrir Square in the heart of the city. They clashed with police along the way, who periodically beat protesters with metal poles.

Protesters set fire to cars and to a fire truck under the 6th of October Bridge. Thick smoke rose above the bridge, stopping traffic and causing panic.

Special correspondent Nevine Bayoumi in Cairo contributed to this report, which was supplemented by wire reports.

Palestinians in Amman, Jordan, flee from clouds of tear gas police fired during a protest against the U.S.-led war in Iraq. Demonstrations were widespread in the Arab world.A Greek Orthodox priest in Athens tries to prevent a demonstrator from throwing a fire bomb at police protecting the U.S. Embassy during a large protest against the war.