Iraq has released about 600 prisoners, the first of 2,500 due to be set free as part of a national reconciliation initiative by the prime minister.
Some said they had barely been questioned by the authorities
Nouri Maliki said those freed would be people with no clear evidence against them or who were arrested by mistake.
More than 100 prisoners were brought to Baghdad by bus, where Sunni Arab politician Omar Juburi welcomed them and gave each one a gift of $200.
About 29,000 prisoners are believed to be held in US- and Iraqi-run jails.
Correspondents say this is expected to be one of the biggest releases of prisoners since US-led forces invaded the country in 2003 to topple Saddam Hussein.
As they stepped out of the buses, some released prisoners wept and kissed the ground while others smiled and waved at waiting relatives.
"You are rejoining society now and you will serve your society and mix again with people," said Mr Juburi, who is the human rights director for the Iraqi Islamic Party.
"We will exert the utmost efforts to release detainees and bring a smile back to prisoners' faces," he added.
Most prisoners are believed to be held on suspicion of involvement in the insurgency that has gripped the country since 2003.
"I spent 16 months in jail without any specific reason. They only questioned me once, accusing me of funding terrorism," said one of the released detainees.
Iraq has been engulfed in sectarian violence since an attack on an important Shia Muslim shrine on 22 February - which has added greatly to the bloodshed of the mainly Sunni-led insurgency.
In the latest attacks:
- Two attacks on police vehicles in Baghdad kill six officers
- A civilian dies when a mortar round hits his house in the Baladiyat neighbourhood of the city. Five bodies are found in various parts of the capital
- Three university students are shot dead by gunmen as they wait at a bus stop in the northern city of Mosul
- A Sunni mosque preacher said to be sympathetic to insurgents is shot in Hawija, northern Iraq
- At least another six people are killed in attacks in Mosul, Tikrit, Kirkuk and Baquba, the AFP news agency reports.
Meanwhile, at least 15 people from a group of 50 who were kidnapped in Baghdad on Monday, had been found alive, police said.
They were sitting together on a street in central Baghdad. Some had been shot in the foot and showed other signs of torture.