Seven people were killed and some 21 wounded in a suicide bomb attack at a coffee shop in central the Iraqi northern city of Mosul Wednesday evening, a local police source told Xinhua. The attack occurred after sunset when a suicide bomber blew up his explosive vest at a coffee shop in Bab Lagash in the central part of Mosul, some 400 km north of the capital Baghdad, the source said on condition of anonymity. One child was among the killed and two policemen were among the wounded, the source said. The predominantly Sunni Arab city of Mosul has long been a stronghold for insurgent groups, including al-Qaida, which fight U. S. troops and Iraqi security forces, since the U.S.-led invasion in 2003. Violence and sporadic high-profile bomb attacks remain common in Iraqi cities despite the dramatic decrease of violence over the past few years.