"An arms depot exploded... The security forces have opened an inquiry to determine the cause," Baghdad's security operations command said in a statement.

A senior police source told AFP on condition of anonymity that the blast was caused by heavy weapons, including rocket-propelled grenades and shells, belonging to an armed group and stored in a house.

He said at least 16 people were killed and some 32 injured in the explosion.

Medical sources confirmed the toll and said that women and children were found among the victims.

Sources said the blast struck near a Shiite mosque in the district of northeast Baghdad.

Witnesses reported heavy material damage to homes and other buildings in the Sadr City district, which is a stronghold of populist Shiite cleric Moqtada Sadr.