A barrage of mortar bombs or rockets hit Baghdad's heavily protected Green Zone, home to the US embassy and Iraqi government, on Saturday, but there were no immediate reports of casualties or damage.

A siren wailed in the Green Zone warning people to take cover amid a series of explosions, Reuters witnesses said.

'I can confirm that we did receive indirect fire and that it was multiple rounds,' said US military spokesman Major Brad Leighton.

The US military has blamed missile attacks on the Green Zone on so-called 'special groups', rogue elements of Moqtada Al-Sadr's Mehdi Army militia they say receives funding and weapons from neighbouring Iran. Iran denies the charge.

On Friday, Sadr renewed a six-month ceasefire which he first called in August to reorganise his splintered militia. The US military welcomed the extension but said it would continue to hunt down the rogue units.-Reuters