And the street battles in Ramadi early on Thursday morning followed numerous and intensified attacks on US forces in Baghdad and Falluja.

Aljazeera has learned that a military base was hit by mortar rounds in al-Dura district in south Baghdad, an attack that developed into a large skirmish around an elementary school close by.

US forces have not confirmed the raid or whether it resulted in casualties. However, Iraqi journalist Haza Afif witnessed a second attack on US forces at Khan Dhari, a town on the road to Falluja.

"A car exploded as a military convoy passed by, resulting in the complete destruction of a troop carrier and an armoured car. There were at least five casualties, one most certainly dead," he said.

Allawi ultimatum

In response to the continuing resistance, US-appointed interim Prime Minister Iyad Allawi threatened a military assault on Falluja unless its residents handed over al-Qaida linked Abu Musab al-Zarqawi.

Allawi said on Wednesday it was high time for Fallujah to return to government control before elections in January.

"We have asked Fallujah residents to turn over Zarqawi and his group. If they don't do it, we are ready for major operations in Falluja," Allawi told Iraq's US-appointed 100-member interim parliament.

German rejection

But at an international level, his ultimatum has received little sympathy. German Chancellor Gerhard Schroeder renewed his firm opposition to deploying troops to help train Iraqi security forces.

His statement slapped down hints at a change in policy from his defence minister.  

The chancellor's comments followed the publication of an interview in Wednesday's Financial Times in which German Defence Minister Peter Struck indicated that Berlin might deploy troops in Iraq if conditions there changed.