BAGHDAD, 30 April 2007 — US forces fired an artillery barrage in southern Baghdad yesterday morning, rocking the capital with loud explosions. The death toll from a suicide car bomb attack in Kerbala rose to 68 as residents dug through the debris of heavily damaged shops.

The blasts in Baghdad came a day after the US military announced the deaths of nine American troops, including four killed in separate roadside bombings south of Baghdad and five in fighting in Anbar province.

American troops also detained 72 suspected insurgents and seized nitric acid and other bomb-making materials during raids yesterday targeting Al-Qaeda in Iraq in Anbar province, a Sunni insurgent stronghold west of the capital, and Salahuddin province, a volatile area northwest of the capital, the US military said.

Iraqis in the southern region of the city said American and Iraqi forces had stepped up their operations in the Dora area of southern Baghdad starting Saturday night.

Authorities in northern Iraq imposed an indefinite curfew in Samarra after leaflets signed by rival insurgent groups threatened policemen if they did not quit their jobs and promised to target any oil company that wants to explore in the area. The warnings to the policemen were signed by Al-Qaeda in Iraq and threatened to destroy their houses if they didn’t comply.

Separately, an Iraqi Sunni lawmaker urged his party to withdraw from the Shiite-led government if it fails to better protect citizens from sectarian bloodshed.

In other developments yesterday, two roadside bombs exploded in separate areas in southeastern Baghdad, killing three civilians and wounding nine, police said.

Gunmen seriously wounded Amal Al-Moudares, one of Iraq’s best-known radio and television journalists, in an attack near her home in Baghdad, police said.