Three policemen sustained serious injuries in a hand grenade attack on a patrol in Sindh capital Karachi late Wednesday, 24NewsHD TV channel reported.
Unidentified motorcyclists hurled a hand grenade at a Sachal police patrol and fled, eyewitnesses said.
They added the attackers wore masks and fled by taking advantage of darkness.
Police, Rangers and other law enforcers reached the spot and shifted the injured to a hospital.
Security has been stepped up and the lawmen have launched a hunt for the fugitives.