Baghdad — Iraqi security forces backed by U.S. troops detained almost 300 suspected insurgents overnight in the largest joint U.S.-Iraqi military offensive to date, the military said Monday.

The Baghdad offensive, dubbed Operation Squeeze Play, came as the American military announced that five U.S. soldiers were killed in northern Iraq on Sunday — four in separate roadside bomb attacks and one in a vehicle accident.

Two carloads of gunmen killed Major General Wael al-Rubaei, a top national security official, and his driver in Baghdad”s latest drive-by shooting. The killing came a day after another senior government official, Trade Ministry auditing office chief Ali Moussa, was shot dead — part of an ongoing terror campaign that has killed more than 550 people in less than one month.

In other violence, a suicide bomber killed five people and injured 13 when he drove an explosives-packed pickup truck into a crowd of people outside a municipal council office in Tuz Khormato, 80 kilometres south of the northern city of Kirkuk, said police commander Lieutenant General Sarhat Qader.