Thirty people were killed and 48 more wounded when gunmen attacked a Sunni Arab neighbourhood of Baghdad today.
It was reported that militiamen grabbed six Sunnis as they left worship services, doused them with petrol and burned them alive as Iraqi soldiers stood by.
Accounts from residents in the Sunni Hurriya district also spoke of two dozen or more dead and homes still ablaze after the attacks, a day after car bombs killed more than 200 people in a Shia district of the city.
Officials said the attackers burned four mosques in the assault as sectarian tensions boiled over in the capital despite a curfew aimed at curbing violence.
Meanwhile, the death toll in yesterday's Baghdad bombings rose to 202 today as another 22 people were killed in a double suicide attack in the northern city of Tal Afar.
In Baghdad, at least 250 other people were wounded in the multiple car bomb and mortar onslaught in the Shia Sadr City slum, the deadliest attack of the entire conflict to date.
It has left political leaders from the Shia majority and the once dominant Sunni community scrambling to appeal for calm.
With Baghdad locked down in indefinite curfew, politicians hope clerical leaders echo those calls in Friday sermons as Muslims go their separate ways to mosques across the city. One renowned Sunni mosque was hit by a mortar round in an apparent retaliatory strike from Sadr City the night before.
In Tal Afar, one bomber drove a car laden with explosives and another blew himself up with a suicide vest, killing 22 people at a market, a police officer in the regional capital Mosul said.
Close to the Syrian border and mostly populated by ethnic Turkish speakers, Tal Afar was once a bastion for al Qaeda-linked Sunni militants but has been held up for the past year by the US military as an example of successful counter-insurgency operations.
Local Sunnis complain, however, of discrimation against them by US-backed Iraqi security forces dominated by Shias.
Barring security forces, the only movement in the streets of the capital was thousands of mourners streaming on foot behind cars laden with coffins as they began their journey south to the holy city of Najaf, traditional burial site for pious Shias.
At Najaf, bodies packed premises set aside near its ancient cemetery for the ritual washing of the dead before interment.
Moqtada al-Sadr, leader of the Mehdi Army militia which dominates Sadr City, also appealed for Iraqis to unite in peace and many in the district, home to over two million people, said they hoped all would control their anger.
Daylight also brought new visions of the mangled metal wrought by six car bombs and a series of mortar blasts that in its turn transformed streets and a market into a bloodbath.
Already, after months of mounting sectarian violence since the destruction of a Shia shrine at Samarra in February, the capital is under curfew for several hours during Friday prayers.
Now the curfew is absolute and indefinite, with Baghdad airport also closed and the key oil port of Basra in the south, controlled by Shia parties, also shutting down.
The United Nations said on Wednesday violent deaths among civilians had hit a record of over 3,700 in October. It said attacks had surged since the Samarra bombing in Febuary and some 420,000 fled their homes to other parts of Iraq since then.
Yesterday's attack was the worst single attack of the war and the highest death toll since 171 people were killed in bombings in Kerbala and Baghdad at Shia ceremonies in 2004.