"After ten minutes, the gunmen took the nine people to a place a few meters (yards) away from the market and opened fire on them," Saad Jawad al-Azzawi said.

Wissam Mohammad al-Ani, a Sunni, said three gunmen stopped him as he was talking toward a bus stop and demanded his identification. They let him go after he produced a fake ID with a Shiite name, but they seized two young men standing nearby.

Police and Shiite leaders speculated the rampage was carried out in retaliation for a Saturday night car bombing at a Shiite mosque that killed two people and wounded nine.

Clashes also broke out between gunmen and Iraqi police in at least three neighborhoods across the capital, police and residents said. Three Shiite militiamen were killed in fighting with security forces in one of them, police said.

The spokesman for a Sunni clerical association, Mohammed Beshar al-Faydhi, blamed the Jihad attack on the Mahdi Army militia, led by radical Shiite cleric Muqtada al-Sadr. Al-Faydhi told Al-Jazeera television that he had documents to prove his allegation.

Al-Sadr denied responsibility and called on both Shiites and Sunnis to "join hands for the sake of Iraq's independence and stability." He assured Vice President Tariq al-Hashimi, leader of the largest Sunni Arab party, that he would punish any of his militiamen if they were involved.

Prime Minister Nouri al-Maliki, a Shiite, has promised to disband Shiite militias and other armed groups, which are blamed for much of the sectarian violence. On Friday, Iraqi troops backed by U.S. jets raided a Shiite militia stronghold in Baghdad's Sadr City neighborhood, killing and wounding dozens of people.

But militias have flourished in large part because of the inability of the police, the Iraqi army and coalition forces to guarantee security. Many in the Shiite majority believe the militias are their only protection against Sunni extremists such as al-Qaida in Iraq, responsible for many car bombings and suicide attacks against Shiite civilians.

The violence is likely to complicate U.S. and Iraqi efforts to encourage disaffected Sunnis to abandon the Sunni-dominated insurgency and join mainstream politics so U.S. troops can begin to go home.

Deputy Prime Minister Salam al-Zubaie, a Sunni, described the Jihad attack as "a real and ugly massacre," and blamed Iraqi security forces, which are widely believed to have been infiltrated by Shiite militias.

"There are officers who instead of being in charge should be questioned and referred to judicial authorities," al-Zubaie told Al-Jazeera TV. "Jihad is witnessing a catastrophic crime."

The prime minister's office quickly distanced itself from al-Zubaie's comments, saying in a statement that they "do not represent the government's point of view."

Sunni politician Alaa Maki also blamed Shiite extremists, claiming they were out to wipe out the Sunni Arab minority.

"We demand the presidency, the prime minister and the parliament stand against this agenda," Maki said. "The situation is very serious. If it deteriorates, all of us will be losers."

Also Sunday, an American soldier died in a "non-combat related incident," the U.S. command said without giving further details.

In the western city of Ramadi, a car bomb exploded next to a U.S. convoy, wounding four American soldiers, the military said. The attack occurred as the convoy headed to the government center in the city, an insurgent hotbed 70 miles west of Baghdad.