Iraqi army soldiers talk with motorists at a vehicle checkpoint in Baghdad, Iraq. The Iraqi capital appeared quieter Thursday, with one reported car bombing and one fatality. A U.S.-led security operation launched Feb. 14 seeks to reclaim Baghdad's lawless streets.

Baghdad, Iraq ? A roadside bomb exploded Thursday alongside the convoy of a prominent Shiite cleric whose high-level political ties have made him the target of past assassination attempts. The imam was not injured, but several bodyguards were wounded.

The attack against Jalal Eddin al-Sagheer, who is also a prominent member of Iraq’s parliament, came on one of Baghdad’s quietest days in months – with one reported car bombing and one fatality.

U.S. and Iraqi forces also neared agreement to expand the Baghdad security sweep into the Shiite stronghold of Sadr City. Such a move would test the willingness of the powerful Mahdi Army militia to grant its American foes access to all parts of Baghdad under its control.

The relative lull in violence offered authorities a rare breather after periods of almost hour-by-hour bombings and mortar strikes by suspected Sunni insurgents.

But the calm was broken after nightfall. The rumbling of artillery fire was heard throughout Baghdad.

In recent days, U.S. gunners have pummeled areas of south Baghdad used as suspected staging grounds for car bombings and other attacks.

There was no immediate word from the military on the latest apparent barrage. Residents said the shelling was concentrated on the mostly Sunni area of Dora.

The barrage highlighted the enormous security challenges of a planned international conference on ways to rebuild and stabilize war-weary Iraq. The gathering hopes to bring together a broad range of Western and Islamic nations, including the United States and pivotal Iraq neighbors Syria and Iran.

Al-Sagheer, an ally of Prime Minister Nouri al-Maliki, said his convoy was attacked in a Sunni area of southwest Baghdad while en route from the airport.

“They targeted me again,” he said, but declined to point the finger at any specific group. He said several bodyguards were wounded.

Al-Sagheer has had close calls in the past that he said were linked to his denunciations of Sunni insurgents and foreign jihadists such as al-Qaida in Iraq.

In June 2006, a shoe bomber killed 10 people during prayers in his mosque in northern Baghdad. Two months earlier, suicide attackers killed at least 85 people as they left the mosque.