U.S. soldiers have captured a former Saddam Hussein regime spy, while a suicide bomber attacked the main checkpoint to Baghdad International Airport on Wednesday, police said, wounding at least seven Iraqis. The explosion, which occurred shortly after 9 a.m. (0500GMT), sent a huge cloud of black smoke billowing into the sky, destroyed several vehicles and underscored the difficulties U.S. and Iraqi authorities are facing to curb the rampant insurgency, according to a report of The Associated Press. In New York, Iraqi Foreign Minister Hoshyar Zebari said U.S.-led forces must stay here until Iraq's own soldiers and policemen can take responsibility for securing the nation amid its continuing insurgency. U.S. soldiers struck a blow against militants plotting attacks by capturing four wanted terrorists during separate raids since Sunday, including a former spy in Saddam's secret service who was believed to be financing several terrorist groups in western Baghdad's Ghazaliyah district, the military said in a statement Wednesday.