Iraqi officials say two car bombs have been found inside the Baghdad office complex used by prominent Sunni politician Adnan al-Dulaimi.

The officials say Iraqi security forces detonated the car bombs, causing damage to Dulaimi's office and surrounding houses, but there were no apparent injuries. Dulaimi leads one of the parties in Iraq's main Sunni parliamentary bloc, the Iraqi Accordance Front.

It was not immediately clear how the car bombs came to be in his complex. Iraqi forces later arrested six of Dulaimi's security guards.

The Associated Press quotes a spokesman for Dulaimi as saying Iraqi forces found and detonated a car bomb near the complex but not inside it.

Dulaimi is a strong critic of Iraqi Prime Minister Nouri al-Maliki, frequently accusing the Shi'ite leader of following sectarian policies.

In another development, several hundred Iraqi refugees returned to Iraq Thursday in a convoy of buses from neighboring Syria. The refugee convoy is the first to be funded by Iraq's government - part of a plan to speed up the return of those who fled abroad.

Twenty buses arrived in Baghdad after being escorted from the Syrian border by Iraqi forces. Iraqi officials who greeted the returning refugees in Baghdad said each family will receive $750 to help in resettlement.

In other developments, the U.S. military said an American soldier was killed Wednesday by small arms fire in Baghdad. The military also said coalition forces detained 12 suspected terrorists during operations Thursday in central and northern Iraq.

The U.S. military said it plans to expand its roster of unofficial Iraqi security guards who act as neighborhood sentries by about 10 to 15 percent. The military already has trained and paid more than 50,000 Iraqis to operate checkpoints in their communities.

Some information for this report was provided by AFP, AP and Reuters.