In recent days, the Iraqi government has freed around 11,000 prisoners. The general amnesty bill specifies offences for which others held without charge can be released.
There are some 50,000 prisoners held in jails around the country, and the number of inmates has increased dramatically since the launch of the US surge in troops early in 2007.
The amnesty is viewed as a crucial step in reconciling Sunni and Shia groups. Sunnis in particular have complained bitterly that many of their citizens have been imprisoned without charge since the invasion of Iraq began.
The US military has indicated it would like to release all prisoners in its care by the end of 2008.