At least 10 people have been killed in the Iraqi capital at a shoot-out near a Sunni mosque, police say.
Suicide attacks in Iraq are at record levels
The incident happened at the al-Mashahada mosque in the Hurriya district, when gunmen opened fire on worshippers attending evening prayers.
Eleven people were wounded in the attack, police said.
The incident came as a US military spokesman in Baghdad, Maj Gen William Caldwell, said that suicide attacks were at the highest level ever.
Gen Caldwell said there had been a spike in violence coinciding with the start of the Muslim holy month of Ramadan, which began on Monday.
"In terms of attacks, this week's suicide attacks were at the highest level of any given week, with half of them targeting security forces," he said. "This has been a tough week."
He said also that Iraqi security forces were "making a concerted effort" to end sectarian violence by targeting death squads in Baghdad.
But the attack on the mosque plays into a situation of acute sectarian tensions which it is bound to aggravate further, the BBC's Jim Muir reports from Baghdad.
The mosque is in a very tense area on the border between Sunni and Shia neighbourhoods.
It has been branded a hotbed of Sunni extremists by hardline Shias, with one of their newspapers referring to it as a car bomb factory and accusing worshippers of shooting Shias last week, our correspondent says.
Parts of the police force have been taken over by militias
The violence came as British and Iraqi forces launched a major drive in Basra city aimed at purging the police of the militias that have infiltrated their ranks.
Shia militias have effectively seized control of the police in some areas.
About 1,000 British troops and 2,300 Iraqis have begun to deploy as part of what the army labels Operation Sinbad.
The operation will see small "transition teams" of Royal Military Police being inserted into police stations throughout the southern Iraqi city for 30 days at a time.
The UK military said the operation, to last until February 2007, was intended to prepare for the expected handover of power to Iraqi officials next year.