KARACHI (AFP) - Pakistan's largest city Karachi shut down on Monday to mourn 45 people killed by a car bomb in a Shiite Muslim neighbourhood, the latest in a series of devastating attacks as Pakistan prepares for elections.

Traffic was thin as educational institutions, businesses and markets closed after the local government announced one day of mourning and Shiite groups three days of mourning for those killed in Sunday's bombing.

The bomb exploded as worshippers were coming out of mosques in the neighbourhood of Abbas Town, ripping through two apartment blocks and trapping people beneath piles of rubble.