BAGHDAD -- Shiite groups brokered a reported cease-fire Saturday with militants fighting U.S. and Iraqi forces in Baghdad's Sadr City as the country's army launched an offensive in Mosul against al-Qaida's main bastion in Iraq.

The bulk of the 60,000-strong Mahdi Army is not believed to have participated in the clashes. Instead the violence is blamed on splinter groups that have refused to honor a general cease-fire ordered by al-Sadr last August. Al-Sadr has directed his supporters to only fight when attacked.

Iraqi government spokesman Ali al-Dabbagh expressed support Saturday for efforts aimed at "achieving order and security in Sadr City."

"The agreement represents the government's vision to end armed displays and purge al-Sadr City from roadside bombs and mines and impose the law in the city," al-Dabbagh said in a statement.

"Iraqi security forces are the only force to achieve this and the government has the right to raid and search any place suspected of possessing heavy or medium weapons," al-Dabbagh said. "The government is also committed to chase all wanted people under the supervision of the prime minister."

There was no immediate comment from the U.S. military on the reported deal.

The newly announced cease-fire comes after government-backed Shiite envoys set strict demands for Shiite militias to end their battles against Iraqi and U.S. forces in a meeting with al-Sadr's supporters on Thursday.

"A 10-point agreement has been reached between members from the United Iraqi Alliance and Sadrist movement in Baghdad and we are informed that Prime Minister Nouri al-Maliki is committed to it," al-Obeidi said in the southern city of Najaf.

He added that "the agreement stipulates that the Mahdi Army will stop fighting in Sadr City and will stop displaying arms in public. In return, the government will stop random raids against al-Sadr followers and open all closed roads that lead to Sadr City."

Al-Obeidi said a joint committee will observe the implementation of the agreement and any violations by either side.

"This document does not call for disbanding al-Mahdi Army or laying down their arms," al-Obeidi said, rejecting a previous call by al-Maliki.

The clashes in Sadr City began in late March after al-Maliki, himself a Shiite, launched a crackdown against the Shiite armed groups in the southern city of Basra. Aid groups say at least 6,000 people have fled the homes in Sadr City to escape the fighting and seek help as food and medical supplies dwindle.

Meanwhile, Maj. Gen. Riyadh Jalal Tawfiq, the commander of military operations in the northern city of Mosul, issued a statement on Saturday to announce that operation "Lion's Roar" against al-Qaida in Iraq was under way.

Mosul is considered the last important urban staging ground for al-Qaida in Iraq after losing its strongholds in Baghdad and other areas during the U.S. troop "surge" last year.

"Operation Lion's Roar is an Iraqi led, planned and executed operation, and is another example of the Iraqis' growing confidence and ability to independently carry out complex combat, police and humanitarian operations," said Maj. Peggy Kageleiry, a spokeswoman for U.S. forces in the north.

She added that U.S.-led Coalition forces "will provide advice, guidance and support as requested by the Iraqi operational commander."

Al-Maliki has been promising a crackdown since last January. But no major offensives have been mounted even as al-Qaida in Iraq tried to exert its influence in Iraq's third-largest city through attacks and intimidation.

• Associated Press writer Hamid Ahmed contributed to this report.