U.S. Defense Secretary Robert Gates on Thursday arrived in Iraq on an unannounced visit, al- Jazeera TV channel reported.
Gates is scheduled to meet with Iraqi political leaders and U.S. military commanders there.
Shortly after he arrived this city, Gates visited a former Sunni Arab insurgent bastion in Fallujah where he would meet the U. S. commander in Iraq.
The report said that Gates' visit is the third to the war-torn country since he took over his post as defense secretary in December.
His visit came a day after a series of bombs rocked Baghdad, killing a total of at least 174 people and wounding more than 200 others, making it the deadliest day in the capital since the launch of a massive crackdown by U.S. and Iraqi forces two months ago.
On Thursday, Gates left from Israel where he had talks with Israeli Prime Minister Ehud Olmert and discussed series of regional issues, especially the nuclear issue of Iran.