Iraqi authorities have freed nearly 600 prisoners after Prime Minister Nouri al-Maliki promised to release 2,500 detainees to foster "reconciliation and national dialogue."
Buses packed with prisoners arrived at Baghdad's central bus station early Wednesday.
Most of the released are members of Iraq's minority Sunni Arab community. Authorities say they were not involved in violent crimes or had been detained by mistake.
Insurgents carried out more attacks across Iraq Wednesday, killing at least 10 people. The dead included six police officers and a Sunni Arab cleric.
Police also say they found alive at least 13 of the 50 men who were kidnapped in Baghdad on Monday. Police say some of them appear to have been tortured. There was no immediate word on the fate of the other kidnap victims or why they were taken.
The mass kidnapping took place in an area of Baghdad where many travel agencies operate. Gunmen wearing police uniforms rounded up businessmen, customers and street vendors in a brazen daytime assault.
On Tuesday, police discovered nine severed heads wrapped in plastic bags near the town of Baquba, northeast of Baghdad in the area of Iraq known as "the Sunni triangle," but that find has not been linked to the kidnapping.
Some information for this report was provided by AFP, AP and Reuters.