"Gunmen are killing Sunni civilians according to their identity cards," an Interior Ministry official told Reuters.

Police and Interior Ministry sources said Shiite gunmen were moving through the predominantly Sunni district of Jihad.

They set up fake checkpoints in the neighborhood and raided many homes.

Firas Shimmari, a security guard, received a call from his brother who reported that the gunmen were checking people's IDs and attacking them if they indicated the person was Sunni.

"They looked at his ID and asked him where he was from and he said (the Shiite holy city of) Karbala, so they told him 'you are fine'," said Shimmari, adding that his brother had seen corpses by the side of the checkpoint.

Another source said Sunni men had been herded into side streets and gunned down.

Iraq has increasingly been plagued by sectarian-linked attacks, especially since the bombing of a revered Shiite shrine in Samarra in February.

Sunni and Shiite holy places were increasingly targeted in the aftermath.

Many Iraqis, Sunnis and Shiites, lined up in droves at state registries over the past few months, believing that name changing is the best protection.

Mehdi Army

"These attacks prove the militias want to drag Iraq into civil war," said Dulaimi.

The finger of accusation was pointed at militias loyal to Shiite leader Moqtada Al-Sadr and Shiites-dominated police, reported Agence France-Presse (AFP).

"I blame the Mehdi Army militiamen for this killing — it is all in the open now," said Sheikh Abdel Samad Al-Obeidi, imam of the Fakhri Shanshal mosque in the neighborhood, which was bombed on Friday killing two.

"Outside the mosque I saw the bodies of 10 men, all shot in the head, and they showed severe signs of torture," he added.

A senior Shiite politician said Mehdi Army fighters from eastern Baghdad had moved into Jihad on Sunday but insisted they were only taking on Sunnis responsible for killing Shiites.

Sheikh Mahmud Al-Sudani, the imam of the Shiite mosque, told AFP the attacks were carried out by relatives of Shiites killed or driven out of the neighborhood in recent months.

"For the past five months Shiites have been killed and evicted from the neighborhood. Those Shiites killed come from tribes from the south that wanted to take revenge," he said.

"There are many terrorist groups in Jihad who are killing Shiite families so they went to fight them," added Sudani, a follower of Sadr.

A few kilometers from Jihad, Reuters staff in Shula, a mainly Shiite island in Sunni west Baghdad, said Mehdi militiamen blocked streets with burning tires and told residents to stay indoors.

The government of Shiite Prime Minister Nuri Al-Maliki has said it will disband Shiite militias, some linked to the police, which Sunnis accuse of running death squads.

"These attacks prove the militias want to drag Iraq into civil war," said Adnan Al-Dulaimi, a leader of the main Sunni parliamentary bloc which is already boycotting parliament over the kidnapping of female Sunni MP Taiseer Al-Mashhadani.

The abductors have demanded guarantees that Shiite mosques and shrines would not be attacked in the future to release the lawmaker, Sunni Vice President Tariq el-Hashimi announced last week.

Police Complicity

Obeidi also accused police commandos, who have checkpoints in the area, of being "complicit in the crime by turning a blind eye".

American and Iraqi troops sealed off the Jihad neighborhood and US helicopters clattered overhead, Reuters reported.

Sunday's rampage came despite a massive security clampdown on the capital over the past four weeks, with tens of thousands of troops patrolling the streets.

The Los Angeles Times, citing Iraqi government documents, said Sunday that the police force is riddled with corruption and its officers have been involved in abductions, murders and prisoner rape.

The confidential Iraqi Ministry of Interior documents, which detail more than 400 police corruption investigations, were authenticated by current and former police officials, said the American daily.

They include reports of Iraqi police participating in bombings and releasing terror suspects for bribes, as well as selling stolen and forged Iraqi passports and beating prisoners to death.

According to the documents, which cover most of 2005 and part of 2006, police elements tortured detainees with electricity, were involved in anal rape and kidnapped Iraqis and demanded ransoms from their families.

In August a female detainee was reportedly raped at a Baghdad detention center by a commander. Two other officers tortured and raped two other detained women, the documents showed.

A separate report in English by private contractors hired by the US State Department to train Iraqi police maintains that "the current climate of corruption, human rights violations and sectarian violence found in Iraq's security forces undermines public confidence."

US officials have known of the police abuses for years but want the Iraqis to solve the problem, officials told the Times.