Baghdad's overnight violence was centred on two bridges linking Tahrir to the western bank of the Tigris, where most government buildings and foreign embassies including the US and Iranian missions are located.

Riot police deployed along the bridges fired tear gas to keep back protesters, who have dug in to their positions with their own barricade.

The protests have evolved since October 1 from rage over corruption and unemployment into a wholesale condemnation of political and religious class and demands for "the downfall of the regime".

Protesters have occupied Tahrir square for more than a week, apparently unimpressed by the government's proposals, including of early elections and a new premier.

"We've been having elections for 16 years, and we've gotten nothing," said Haydar, 30, a protester in Tahrir.

Another activist, Mohammad, 22, said the demonstrators should not accept such "fake reforms".

"People are very aware of what's happening: we've gotten to an important phase and can't lose it all now," he added.

Since October 1, more than 250 people have been killed and thousands more wounded in the rallies.

The latest official toll was provided on Wednesday, but medical and security sources said at least eight demonstrators have been killed since.

Seven of them died around Tahrir, where clashes between riot police and security forces have escalated.

The eighth victim was killed by the security guards of a local politician in the southern city of Nasiriyah.

Rights group Amnesty International slammed Iraqi forces this week for using two types of military-grade tear gas canisters that have pierced protesters' skulls and lungs.