According to the police officials quoted by Efe news agency the explosion happened late on Wednesday inside a house used as a depot for weapons and ammunition which was destroyed along with three other homes while a nearby Shiite mosque was damaged.
Previously the police had attributed the explosion to a car bomb which was believed to have been stationed in this popular Shiite neighbourhood a frequent scene of such attacks.
Muqtada al-Sadr is the leader of the Sairun alliance the majority winner in the Iraqi parliamentary elections of May 12.
The explosion occurred a few hours after the Iraqi parliament ordered a manual recount of votes due to suspicions of fraud and falsification.
--IANS ahm/mr
