KARACHI, Pakistan (AP) — Police say a bomb planted in a hollow concrete block has killed two police officers and injured nine other people in southern Pakistan.

Senior police officer Alilm Jaffery says the victims responded to a report of an explosion near a garbage bin Thursday evening and then were killed by the second blast after they reached the scene in eastern Karachi.

There has been an uptick in violence in Karachi, including several such twin explosions.

Jaffery says two of the injured officers died on the way to the hospital and a third is in critical condition.

A police patrol vehicle and two ambulances were damaged in the blast.