The Iraqi authorities have extended until Monday a curfew imposed on Baghdad in response to recent killings.
There are reports of mortar fire in Baghdad despite the curfew
The measure was intended to prevent reprisals for bomb attacks on the Sadr City area which killed more than 200.
Violence continued across Iraq however, with 21 bodies found in a village north of Baghdad. US and Iraqi forces said more than 50 insurgents died in raids.
President Jalal Talabani has also had to postpone a much-anticipated trip to Iran, as Baghdad's airport is closed.
Mr Talabani had been due to meet Iranian President Mahmoud Ahmadinejad for talks on Iraq's security situation.
A spokesman for Mr Talabani said he would travel when the airport re-opened.
Separately, US Vice-President Dick Cheney has arrived in the Saudi capital, Riyadh, for talks with King Abdullah on the situation in the Middle East, particularly Iraq.
Despite the heavy police presence in the capital, there were reports that the Shia Sadr City district had been hit by a barrage of mortars on Saturday, says the BBC's Andy Gallacher in Baghdad.
An Iraqi journalists living in the area said he had heard 12 explosions but there have been no immediate reports of casualties, our correspondent adds.
The US military said the 22 insurgents killed by its forces had died in clashes to the north of Baghdad.
Moqtada Sadr's group is calling for US forces to leave
Ten insurgents died in a raid on a bomb-making factory in the town of Taji, it said, while a teenage boy was killed in the crossfire and a pregnant woman was wounded.
US forces said they had discovered caches of rocket-propelled grenades, machine guns, pipe bombs and anti-aircraft weapons in the area. These were later destroyed in an air strike.
In another incident, US forces said they had killed 12 insurgents in a convoy of cars that ignored warning shots.
Iraqi security services said they had killed more than 30 insurgents in a series of raids in Diyala province.
Earlier in the day, the bodies of 21 Iraqis were discovered in the same province, in a village about 80km (50 miles) north-east of Baghdad.
Police said gunmen had raided the homes of two Shia families, dragged out 21 males and shot them dead. It is thought the youngest victim was a 12-year-old boy.
In central Anbar province, a suicide car bomber attacked a checkpoint and killed three Iraqis, two of them children, and a US serviceman, the US military said.
Cycle of attacks
Meanwhile, leading Sunni cleric Harith al-Dhari, head of Iraq's Association of Muslim Scholars, called on Saturday for Arab countries to withdraw their recognition of the Iraqi government.
Mr Dhari, who spoke in Cairo, faces questioning if he returns to Iraq for allegedly inciting sectarian violence.
Earlier this week, at least 230 people were killed in two days of violence in Baghdad.
In one incident, gunmen attacked Hurriya, a Sunni Arab area of Baghdad, burning mosques and homes, and at least 30 people were reported killed.
Several blasts struck Sadr City in quick succession
The attacks were in apparent revenge for Thursday's bombings that killed more than 200 people in the Shia Sadr City district.
There is a real feeling that the situation is moving to the brink amid the cycle of attacks, says the BBC's David Loyn in Baghdad.
To add to the Iraqi government's woes, a key Shia group loyal to cleric Moqtada al-Sadr threatened to quit parliament and the cabinet if the prime minister goes ahead with a planned meeting with US President George W Bush next week.
The withdrawal of the group headed by Mr Sadr would deal a major blow to an already unstable government.
In a sermon on Friday, the young cleric appealed for Muslim unity, but also demanded that the leading religious figure from the Sunni minority issue a fatwa against al-Qaeda members.
Moqtada al-Sadr's Mehdi Army militia dominates the sprawling Sadr City slum in east Baghdad.
Thursday's multiple car bomb attacks in Sadr City - in which 250 people were also wounded - were the deadliest in Iraq since the US-led invasion of 2003.