BAGHDAD, Iraq — U.S. forces released about 320 Iraqi prisoners from the scandal-ridden Abu Ghraib prison on Sunday.
Meanwhile, violence in Iraq continued Sunday, with bomb blasts killing at least 21 people in a car bombing at a military base north of Baghdad and at an Iraqi police station 40 miles to the south.
But the streets reportedly remained calm in Najaf, where the Mahdi Army, a militia loyal to the radical Shiite cleric Muqtada al-Sadr, began withdrawing on Saturday as part of a peace deal worked out with U.S.-approved Shiite clerics. Hopes that the quiet in the streets could last were raised on Saturday when al-Sadr met with Iraq's most revered Shiite cleric, Grand Ayatollah Ali al-Sistani.
Still, in Sadr City, the Baghdad slum named after al-Sadr's father, gunmen shot at and then blew up a police station that was apparently unoccupied at the time. The police station had earlier been taken over by the U.S. Army. Around Baghdad, there was speculation on Sunday that armed fighters returning from Najaf and nearby Kufa could spark a surge in violence here in the capital.
Those concerns were intensified by the possibility that insurgents might try to disrupt the transfer of power from the U.S.-led occupation to a newly appointed Iraqi government on June 30.
After dark on Sunday, two large explosions were heard in central Baghdad. The causes could not be immediately determined.
Also on Sunday, the private security firm Blackwater USA confirmed that four civilians, two Americans and two Poles, who were killed in an attack on the main road from Baghdad on Saturday were employees of the company. The killings of four Blackwater employees in Fallujah in March provoked an invasion of the town by occupation forces.
The release from Abu Ghraib prison began at 8 a.m., and a series of buses carrying the former detainees left the site during the day as local sheiks stood by. The prison, west of Baghdad, was the scene of photographs of Iraqi prisoners being humiliated and abused that became public in April. An occupation spokesman said that about 320 prisoners were released from Abu Ghraib during the day and that 3,100 remained under detention.