An Afghan official says a massive car bomb has killed seven people and wounded 20 in an attack on the governor's compound in Helmand province.

Provincial police chief Nabi Jan Mullahkheil says the blast in the volatile southern city of Lashkar Gah on Wednesday happened when a suicide bomber detonated a car full of explosives at the back wall of the governor's compound and the adjacent residence of the head of the provincial council.

He says the governor's spokesman, Omar Zwak, was wounded. Zwak was in his office at the time and has been hospitalized.

No one has claimed responsibility yet for the blast. Taliban insurgents have been under pressure from an army offensive in northern Helmand and appear to be retaliating with attacks on Lashkar Gah.