"Nine civilians were killed and 13 injured" when the tanker exploded, the commander of security forces in Baghdad, Ahmad Salim, said in a statement.

"The explosion is an accident and not an act of terrorism," he added.

A medical source told AFP 12 were killed. Another medical source had previously told AFP there were "eight dead and 20 injured".

The explosion, heard across much of Iraq's capital, was in a car park near a football field in a residential area of eastern Baghdad.

An AFP correspondent said the windows of nearby buildings were blown out and vehicles in the area were damaged.