An al-Qaida front group said Sunday that it had captured several US soldiers in the attack a day earlier south of Baghdad that killed five and left three missing. The US said 4,000 troops were searching the farming area south of the capital for any sign of the three missing American soldiers. In a statement posted on an Islamic Web site, the Islamic State of Iraq, claimed responsibility for the attack in Mahmoudiya on Saturday and said it held an unspecified number of US soldiers. The group offered no proof to back up its claim but promised more details later. Meanwhile, a suicide truck bomber crashed into the offices of a Kurdish political party on Sunday, killing at least 50 people and wounding scores, including a mayor, officials said. It was the second suicide attack in Kurdish areas of the north in four days. A parked car bomb also exploded near a market in central Baghdad on Sunday, killing at least 17 Iraqis, wounding 46 and damaging shops, police said. The 10:30 a.m. suicide truck bomb attack in Makhmur, 50 kilometers (30 miles) south of Irbil, badly damaged the office of the Kurdistan Democratic Party of Massoud Barzani, leader of the autonomous Kurdish region in northern Iraq. Makhmur is just south of the autonomous Kurdish-controlled areas, but it has a substantial Kurdish population. The blast also killed the police chief and damaged the mayor's office, officials said. Ziryan Othman, the health minister of the Kurdish regional government, said at least 45 people were killed and 115 were wounded, including the city's mayor, Abdul Rahman Delaf, who also is a prominent Kurdish writer, and the director of the KDP office.