Gunmen burst into Samarra's Golden Mosque Wednesday morning, one of Iraq's four holiest Shi'ite sites, and used explosives to bring down its 100-year-old gilded dome, among the biggest in the Muslim world, Iraqi senior officials said. No casualties were reported.

Many people in Samarra, 120 km north of Baghdad, took to the streets in protest against the attack and chanted slogans against the US troops, terrorism and the Iraqi government, which they accused of failing to bring security and stability to the violence-torn country.

Iraq's Grand Ayatollah Ali al- Sistani was shown on television meeting fellow senior Shi'ite clerics Wednesday in an all but unprecedented appearance by the top religious authority after the attack on the Shi'ite shrine.

Al-Forat television, run by a Shi'ite political party, showed the ageing and reclusive Sistani flanked by his three most senior colleagues in the holy city of Najaf after Sistani called for peaceful protests following the attack in Samarra.

The Iraqi president said the attackers wanted to derail efforts to form a national unity government. Iraq's national security adviser accused al Qaida-inspired Sunni militants of blasting the Shi'ite shrine to foment civil war. There was no immediate claim of responsibility.

An Interior Ministry spokesman said the attackers wore police uniforms, tied up the mosque guards and set the charges.

National Security Adviser Mowaffaq al-Rubaie, a Shi'ite, who blamed the attack on al-Qaida, told state television 10 suspects had been arrested. "They will fail to draw the Iraqi people into civil war as they have failed in the past," he said.

As gunmen attacked Sunni mosques, Prime Minister Ibrahim al-Jaafari, a Shi'ite, declared three days of mourning and called for Muslim unity. He said the interim government had sent officials to Samarra, 100 kilometers north of Baghdad.

Security forces sealed off the mainly Sunni city and police said they had fired over demonstrators' heads at one point as they chanted religious and anti-American slogans.

Top Sunni political leader Adnan al-Dulaimi urged Jaafari to impose a curfew to protect Sunnis and accused Shi'ite gunmen of killing a Sunni cleric in Baghdad.

Abdul Aziz al-Hakim, powerful leader of the Shi'ite SCIRI party, which has its own armed wing, said: "The great Iraqi people will not keep silent over this grave crime."

Iraqi President Jalal Talabani, a Sunni Kurd, also condemned the attack.

In the mainly Shi'ite city of Basra, police said gunmen fired on the office of the main Sunni political group, the Iraqi Islamic Party. Witnesses said rocket-propelled grenades damaged a Sunni mosque in the city. A reporter said Sunni and Shi'ite gunmen were trading heavy fire.

Police said an Iraqi Islamic Party office was burned on the outskirts of Baghdad.

Gunmen fired on a Sunni mosque in Baghdad's Ghazaliya district and burned its gate, police and witnesses said. A Sunni clerical group said three Baghdad mosques were fired on. A Sunni cleric said rocket-propelled grenades hit mosques in the eastern area of Baladiyat. Iraqi troops prevented journalists reaching the scene. Some similar reports turned out to be false.

Thousands of people marched in Shi'ite towns across the country and through the capital, condemning the Samarra attack.

Black-clad militiamen of the Mehdi Army, loyal to Shi'ite cleric Moqtada al-Sadr, were out in force in Shi'ite strongholds like Sadr City in Baghdad and the southern city of Samawa.

US officials, most recently Ambassador Zalmay Khalilzad on Monday, are pressing Jaafari to form a cabinet with support across the nation to avert the threat of a civil war that could thwart Washington's efforts to withdraw its 130,000 troops.

Jaafari angrily dismissed the envoy's intervention.

Sunni rebels are strong in Samarra and there have been attacks recently on Shi'ite pilgrims visiting the shrine to the revered 9th-century Imam Ali al-Hadi and his son, Imam Hassan al-Askari. Shi'ite websites said relics of the buried imams, including a helmet and shield, were damaged in the explosions.

Outside Grand Ayatollah Sistani's office, where he was meeting his most senior colleagues, 2,000 demonstrators chanted: "Rise up Shi'ites! Shi'ites take revenge! Rise up Shi'ites!"

"For the Shi'ites ... this is a major assault comparable to an attack on Mecca for all Muslims," said Hazim al-Naimi, a political science professor at Baghdad's Mustansiriya University. "We will definitely see more sectarianism after this attack ... It could push the country closer to civil war."

(China Daily, Xinhua News Agency February 23, 2006)