At least four people were killed and 17 others were injured when a truck rigged with explosives struck a police station in the northern city of Mosul on Tuesday, a local police source said.

"A suicide bomber drove his explosive-laden truck into the police station of the Mahatta neighborhood in southwestern Mosul," the source told Xinhua on condition of anonymity.

Among the victims were three policemen killed and nine others injured, the source said.

Nineveh province, with its capital city of Mosul, some 400 km north of Baghdad, is said to be one of the last strongholds of al- Qaida fighters and other insurgent groups in the war-torn country.

Despite security gains in recent months in Iraq, there are still sporadic bombings targeting U.S. troops, Iraqi security forces and civilians, which shape setback to the Iraqi government.

(Xinhua News Agency March 31, 2009)