Iraqi policemen stand by seized anti-tank mines Saturday at their station in Baghdad. Police discovered a cache of 600 anti-tank mines in a raid in the Shiite enclave of Sadr City in Baghdad on Saturday.

Baghdad, Iraq ? Suicide bombers struck in force across Iraq on Saturday, killing at least 46 people and wounding scores more in an explosion of street violence after days of relative calm.

In the worst attack, a man posing as the driver of a truck loaded with bricks detonated a huge bomb at a police station under construction in the south Baghdad neighborhood of Dora, a Sunni insurgent stronghold.

The explosion sent shockwaves through the city, with people as far away as the heavily fortified Green Zone several miles to the north thinking it had struck nearby. A black column of smoke billowed from the site of the attack and drifted westward in the cloudy sky.

Witnesses said the driver detonated his charge after he was stopped at a security gate entering the police compound. Still, they said, the building was virtually demolished. There were reports that medical aid and rescue workers responding to the blast were fired on by insurgents around the station.

Other reports indicated the facility sometimes is used by joint Iraqi and American forces, but no Americans were present at the time of the attack. Lt. Col. Christopher Garver, a spokesman for the U.S.-led military forces in Iraq, said the outpost is not one of the new “joint security stations” that are a fixture of the new security plan.

A group calling itself the Islamic State of Iraq, which is composed of al-Qaida in Iraq and other insurgent fighters, claimed responsibility for the Dora police station bombing in a posting on the group’s Web site. The claim could not be confirmed.

Police said at least 20 people were killed, although the number continued to increase throughout the day as rescuers dug through the remains of the building. Among the confirmed dead were 14 police officers and three prisoners, who were killed when the building collapsed.

Police and civilian witnesses said American artillery units in south Baghdad began shelling date palm orchards in the area in the afternoon. Insurgents frequently use the orchards as hiding places and staging grounds for attacks on security forces and, recently, Shiite pilgrims on their way to Karbala for religious ceremonies.

South of the city, near Hillah, a second truck bomb explosion near a Shiite mosque that also houses a political office of radical cleric Muqtada al-Sadr killed 10 and hurt more than 30. The blast also severely damaged the building.

Another suicide bomber walked into a candy store in the northwestern city of Tal Afar and blew himself up, killing 10. Three more struck checkpoints and a police station on the northwestern border with Syria, killing six.

The U.S. military on Saturday also disclosed the death of a soldier who was killed by a roadside bomb while on a foot patrol in south Baghdad the day before.

Also, four people were killed by mortar shelling in a poor Shiite slum in east Baghdad, and two civilians were killed in crossfire between insurgents and the Iraqi army in central Baghdad. Police reported finding the bodies of 10 men on the streets of Baghdad who had been shot to death, and Iraqi troops in the western city of Fallujah found the bodies of 10 men killed execution-style.