At least six people have been killed and 38 others wounded after two mortar rounds struck a square filled with Shia pilgrims in Iraq's capital.

The attack on Sunday took place in Quraish Square in Baghdad's northwestern Kadhimiya district, where pilgrims were gathering ahead of a religious festival to mark the death anniversary of the Shia Imam Moussa al-Kadhim.

Police sources said the death toll could rise.

An interior ministry source said security forces had been put on high alert and that a tight security belt was in place around Kadhimiya in a bid to prevent further attacks on pilgrims walking towards the Imam Kadhim shrine.

A vehicle ban, excluding emergency vehicles such as ambulances, would also be imposed in Kadhimiya from Monday and anyone entering the area would be searched, police sources said.

Although overall violence in Iraq has dropped, Sunni Islamist fighters with links to al-Qaeda are still capable of lethal attacks and often hit Shia targets to stir up the kind of sectarian pressure that almost led to civil war in 2006-2007.