ABU GHRAIB, Iraq, AP – The U.S. military freed 500 Iraqi detainees from Abu Ghraib prison on Monday, a goodwill gesture requested by the Iraqi government ahead of the Muslim holy month of Ramadan.

Another 500 will be released later this week, the military said.

The first batch was loaded onto Iraqi public buses and driven out of the notorious prison in the morning.

The U.S. government said it only releases detainees who are not guilty of serious, violent crimes — such as bombing, torture, kidnapping, or murder — and who have had admitted their crimes, renounced violence, and &#34pledged to be good citizens of a democratic Iraq.&#34

Arab governments often pardon nonviolent offenders during the Ramadan, which is expected to begin on Oct. 4 or 5. Senior Muslim clerics determine the start of the holiday based on their observations of the moon.

But Monday”s action, and the release of 1,000 other Abu Ghraib detainees last month, also appeared to be part of a government effort to persuade Iraqis to vote in the Oct. 15 referendum on a proposed constitution, especially the Sunni minority.

Sunni representatives involved in drafting the constitution had demanded the release of thousands of prisoners who have been languishing in the jail for months without being charged. President Jalal Talabani agreed, and Sunni negotiator Saleh al-Mutlaq said most of the detainees to be freed from Abu Ghraib would be Sunni Arabs.

Iraq”s Sunni-led insurgency and Sunni leaders are calling for a boycott or a &#34no&#34 vote in next month”s referendum.

Many Sunnis believe the constitution will give too much power to Shiites and Kurds.

Under Saddam Hussein, Sunnis held most of the power, but the current Iraqi government, elected in January, is mostly controlled by Kurds and majority Shiites.

Abu Ghraib prison, built by Saddam”s regime in the 1970s on the outskirts of Baghdad, was retained as a major detention center by the U.S. occupation authorities after the occupation of Iraq in 2003.

It gained international notoriety after a number of U.S. military personnel were charged with humiliating and assaulting detainees at the facility.