Mourners carry the body of Fadhil al-Akil to his burial in the Shi'ite holy city of Najaf, Friday

Iraqi police say gunmen have killed an aide to the country's most revered Shi'ite cleric, in the latest attack on his associates.

Police say Grand Ayatollah Ali al-Sistani's aide, Sheikh Fadhil Aqil, was killed late Thursday in a drive-by shooting outside his home in the Shi'ite holy city of Najaf.

Last month, another aide, Sheikh Abdullah Falak, who collected religious taxes for Sistani was stabbed to death in Najaf.

In statements issued Friday, the U.S. military in Iraq said four American soldiers were killed during combat operations in Baghdad.

The military said a roadside bomb blast killed three soldiers and wounded 11 others in eastern Baghdad late Thursday. Earlier, the military said one soldier was killed and three wounded while conducting operations in a western section of the Iraqi capital.

The U.S. military also announced that 17 suspected insurgents were detained today in raids targeting al-Qaida in Iraq along Iraq's Tigris River.

In other news, the Iraqi government said Prime Minister Nouri al-Maliki will visit Turkey on Tuesday and Iran on Wednesday. A spokesman for Mr. Maliki said the prime minister's meetings in both countries will focus on security issues. Discussions in Ankara will address Turkish concerns about Kurdish rebels operating out of northern Iraq.