Updated

U.S. troops on Tuesday joined Iraqi forces and police in patrolling a city north of Baghdad where a surge in sectarian fighting had killed at least 91 people. American and Iraqi officials said the bloodletting in Balad had eased, although some violence continued.

Unidentified gunmen in police uniform, however, hijacked 13 civilian cars with their occupants at Sayed Gharib checkpoint 7 kilometers outside Balad on Monday night, an officer at the Salahuddin provincial police headquarters said.

He said the incident took place after police had left the checkpoint. Those abducted had been taken to another neighborhood nearby but there was no further word on their fate. The officer spoke only on condition of anonymity because he wasn't authorized to talk to media.

Click Here to Visit FOXNews.com's Iraq center.

By Tuesday morning, the U.S. military said in a statement that American forces had responded to Iraqi requests to back up security forces in the town, which lies near a major U.S. air base an hour's drive north of the capital.

As the violence had raged over the weekend, the American military initially said it had not been asked for help. By Monday, the military indicated some involvement but issued only a vague state.

The final and more difinitive but still imprecise description of U.S. involvement was issued by Tuesday.

CountryWatch:Iraq

"By coordinating all of our efforts, we have seen a marked decrease in violence in the past 24 hours," Martindale said, adding that U.S. forces were also firing back at insurgents launching mortar attacks on civilians in the area, said Lt. Col. Jeffery Martindale, commander of 1st Battalion, 8th Infantry Regiment, 4th Infantry Division.

Martindale also said U.S. troops detained a pair of Iraqi police officers in the neighboring Sunni town of Duluiyah. The men were suspected of being involved in the slaying of 17 Shiite Muslim workers last week that sparked a wave of revenge killings by Shiite militiamen, Martindale said.

That announcement reflects claims that local security forces have aided both sides in the sectarian fighting. Sunnis fleeing Balad across the Tigris River to Duluiyah said Shiite police in the city had teamed up with death squads who killed at least 74 Sunnis.

Hadi al-Amiri, the head of the Iraqi parliament's security committee, said Balad was being blockaded to prevent more fighters from entering.

"There are still painful incidents in there," said al-Amiri, a key member of the Supreme Council for the Islamic Revolution, Iraq's main Shiite religious party.

Hearings resumed Tuesday in the trial of former dictator Saddam Hussein and six members of his regime charged with war crimes and crimes against humanity during a military offensive against Iraq's Kurdish population in 1987-88. Saddam and one other defendant are also charged with genocide.

A Kurdish witness — Mutalib Mohammed Salman, 78 — told the court that his wife and 32 relatives disappeared in 1988 after troops overran his village in northern Iraq. The bodies of his wife's body and the remains of two other relatives were found in a mass grave after Saddam's regime was toppled in 2003, he said.

Click Here to Visit FOXNews.com's Iraq center.

The prosecution says about 180,000 people, mostly civilians, died in the offensive, codenamed Operation Anfal. If convicted, the defendants could be sentenced to death by hanging.

Across Iraq, bombings and shootings killed at least 32 people.

Ten people were killed in a spate of shootings in the southern, predominantly Shiite city of Basra, 340 miles southeast of Baghdad.

Unidentified gunmen in both police and civilian vehicles gunned down victims including four students outside the city's university and a well-known doctor who was leaving her house for work, said a Basra police captain speaking on condition of anonymity for fear of reprisals.

In Karmah, 80 kilometers west of Baghdad, a roadside bomb killed five Iraqi soldiers as their convoy passed through the town at 7:00 a.m., police Lt. Ahmed Ali said.

Gunmen stormed into the house of a Shiite family in Balad Ruz, 45 miles northeast of Baghdad, at 3:00 a.m., killing the mother and four adult sons and injuring the father, provincial police official Khalil Yacoub said.

Two policemen in a patrol car were killed at 11:00 a.m. by gunmen in a passing car in the center of the western city of Falluja, a former insurgent, police Lt. Husam Mohammed said.

In the northern city of Mosul, gunmen killed a member of the Patriotic Union of Kurdistan, one of two main Kurdish political parties, police Brig. Saed Ahmed said. Gunmen approached by car and fired at Fatah Hurki at 8:30 a.m as he stood in front of his home in the al-Shurta section of Mosul, 225 miles northwest of Baghdad, Ahmed said.

Also in the heavily Kurdish north, two suicide car bombers blew themselves up in a botched attack at about 5:00 a.m. near the police academy in Kirkuk, police Brig. Sarhat Qadir said. There were no reports of other casualties in the attack. A suicide bomber attacked a Kurdish girls' high school in Kirkuk on Sunday as part of a string of attacks that killed at least 10 people in the ethnically mixed city.

Three guards attached to the head of the city council in Samarra were shot dead by unknown gunmen while refueling at gas station in the city, 60 miles north of Baghdad, police Capt. Laith Mohammed said.

Unidentified gunmen attacked a facility belonging to the central Euphrates electricity distribution authority in the town of Hillah, about 60 miles south of Baghdad, killing a technician and wounding five guards.

Elsewhere in Hillah, gunmen raided a house of a local vehicle merchant at 7:00 a.m. and kidnapped one of his sons, police Capt. Mothana Khalid Ali said.

In Baghdad, two people, including a policeman, were killed and four wounded in a mortar attack on the downtown Ilwiyah neighborhood, police Lt. Bilal Ali Majid said.

Twenty people were injured when two Katyusha rockets landed on Baghdad's violence-torn Dora neighborhood, police Capt. Firas Geiti said. One policeman was killed and three injured in a car bombing in the neighborhood, police Lt. Maitham Abdul-Razaq said.

Four people traveling in a car were injured by a roadside bomb that targeted but missed a police patrol in east Baghdad's Zayouna neighborhood, Capt. Mohammed Adul-Ghani said.

The blindfolded and bound bodies of two unidentified men were found dumped in west Baghdad early Tuesday, Abdul-Razaq said. Abdul-Razaq said the men had been shot in the head and their bodies showed signs of torture — a calling card of roving sectarian death squads blamed for nightly killings and abductions.

There were no new reports Tuesday of U.S. casualties in Iraq. Seven American troops died in fighting Sunday, raising the U.S. toll to 58 killed in the first two weeks of October, a pace that if continued would make the month the worst for coalition forces since January 2005.

Iraqi deaths also are running at a high rate. According to an Associated Press count, 708 Iraqis have been reported killed in war-related violence this month, or just over 44 a day, compared to a daily average of more than 27 since the AP began tracking deaths in April 2005.