US and Iraqi troops clashed with gunmen in a Sunni insurgent stronghold north of the heavily fortified Green Zone on Wednesday, and officials said at least one civilian was killed and nine suspected insurgents were captured in the fighting. Black smoke rose from the area, about two kilometers north of the Green Zone, site of the US and British embassies as well as the Iraqi government headquarters. Apache attack helicopters buzzed overhead. The US military said Iraqi army and American soldiers had launched targeted raids to clear the area of militants in an operation dubbed Tomahawk Strike 11. "Iraqi army and Multi-National Division - Baghdad soldiers commenced a pre-planned security operation early this morning on Haifa Street," the military said in a statement, adding the operation was aimed at restoring Iraqi security force control in the area. It did not give more details. The clashes broke out as US and Iraqi troops gear up for a broader security crackdown to quell the sectarian violence in the capital. Television News footage showed the helicopters flying past high-rise concrete buildings, with several Hummers on the tree-lined street below. Heavy gunfire also could be heard in the background as shells fell, and at least five Srykers were seen leaving the street. The fighting between coalition forces and attackers armed with machine guns, rocket-propelled grenades and mortars started about 5 a.m., witnesses said. A spokesman at the Cultural Ministry, Jabbar al-Mashhadani, told The Associated Press that US and Iraqi forces rushed into the building on the edge of Haifa Street at 9 a.m. and told all the employees to go home as they fanned out and sent snipers to the roof. Six insurgents with automatic weapons and some bombs and three other suspects were arrested near a secondary school in the area, an Iraqi army official said, speaking on condition of anonymity because he was not authorized to disclose information about the operation. At least one civilian was killed and seven others were wounded due to the clashes, which began on a smaller scale on Tuesday, according to hospital and police officials.