A US military base in northern Iraq has come under heavy attack, leaving at least 22 people dead and up to 50 more wounded. The Tuesday assault targeted a canteen used by soldiers in Forward Operating Base Marez southwest from the city of Mosul. In an unverified website statement, an Iraqi group - Ansar al-Sunna - said it carried out the multiple rocket and mortar attacks. A defence official at the Pentagon has confirmed the toll, but said it was unclear how many US troops were among the casualties in the lunch-time attack. The US military in Iraq issued a statement which verified the time of the noon strike, when the canteen would have been at its most crowded, and said an investigation was under way. Witnesses said two or three explosions hit the camp - the biggest base in the region - and that they saw smoke rising from around the airfield. Major General Carter Ham, the commander of the 8,000 US troops based in Mosul, said the dead included U.S. soldiers, U.S. and foreign contractors and members of the Iraqi army. "More than 20 have been killed and more than 60 people have been wounded," he said, adding there was a single explosion. **US attacks*** The raid came as US warplanes launched air strikes on the Iraqi town of Hiyt, west of the capital, killing six Iraqi civilians and wounding nine others. Hospital officials said a woman and child were among those wounded in the strikes which began on Monday night on the Jamaiya and al-Sinai districts on the eastern edges of the town, which lies about 170km west of Baghdad. Aljazeera learned that houses, shops and vehicles belonging to civilians were destroyed in the bombing that continued until Tuesday morning. US marines based in the area had no immediate comment. Hiyt is situated in the tense Anbar province, which includes Falluja, where US-led forces launched a major offensive last month to target fighters opposed to the US-led interim government. **US troops wounded*** A roadside bombing in northern Iraq wounded five US soldiers and an Iraqi civilian, the US military said on Tuesday. The bombing near Hawija, west of the northern oil city of Kirkuk, occurred at 11.15am (0815 GMT) on Monday, the military said in a statement. The six were travelling in a vehicle that was hit by the bomb. They were listed as being in a stable condition. One suspected bomber was detained, the statement added. Meanwhile, four suspected anti-US fighters were arrested in Awja, the hometown of ousted president Saddam Hussein, just south of Tikrit on Monday night, the military said. **PHOTO CAPTION*** Workers and U.S. soldiers tend to the wounded after an apparent insurgent mortar attack on a dining facility during lunchtime on FOB Marez in Mosul, Iraq on Tuesday, Dec. 21, 2004. (Richmond Times-Dispatch/ Dean H)