Five Iraqis have been killed and 17 injured by a bomb planted outside a Sunni mosque in the town of Khalis, 60km (40 miles) north-east of Baghdad.
Hundreds of Iraqis have been killed in violence during the past month
Earlier, a series of insurgent attacks in the capital left seven other people dead, including three policemen.
Police also discovered the bodies of seven men in the city's east. They had been handcuffed and shot in the head.
The violence came as US Defence Secretary Donald Rumsfeld urged Iraqi leaders to form a new government.
In what appeared to be the latest in a series of sectarian killings which has stricken the country since the bombing in February of a Shia shrine in Samarra, a bomb was planted near the entrance of the Saad Bin Abi Waqqas mosque in Khalis, 60km (40 miles) north-east of Baghdad.
The bomb exploded as worshippers left the mosque after Friday prayers.
Police told the BBC that US forces were in the vicinity of the mosque earlier, but had left by the time prayers ended.
In Baghdad, four people were killed when gunmen raided a bakery in the predominantly Sunni district of Saidiya.
A policeman was killed soon afterwards by a bomb that the attackers had left behind.
Two other policemen were shot dead in an ambush in the city's west.
Earlier, the bodies of seven men were found by police in Canal Street in eastern Baghdad.
The victims had been handcuffed, blindfolded and shot in the head.
The men have not been identified, but they were all wearing civilian clothes.
More than 30 people were killed, many of them policemen, and dozens wounded in a series of bomb attacks in Baghdad on Thursday.
Speaking to reporters before the attacks, Mr Rumsfeld urged Iraqi leaders to form a government that included all of the country's religious, ethnic and political groups.
"A good government, a competent government, a government that's seen as inclusive and seen as governing from the centre, that gets about the task of serving the Iraqi people... I believe that that would be a good thing for the country and would reduce the level of violence," he said.
"So to the extent that isn't happening, obviously, the level of violence continues and people are being killed, and that's unfortunate. And they need to get about the task."
On Sunday, Iraqi leaders formed a security council to tackle key issues while talks on forming a new government continued, but there has been no sign of progress since.
There has been deadlock over the post of prime minister, with the Shia-led United Iraqi Alliance's potential coalition partners rejecting its candidate - the incumbent - Ibrahim Jaafari.
The UIA won the right to nominate someone for the premiership after taking 128 out of 275 seats in Iraq's new parliament, the Council of Representatives, in the 15 December elections, 10 seats short of a majority.