U.S. soldiers arrested five suspected members of a death squad south of Baghdad on Wednesday as the U.S. military prepared to reinforce its ranks in the capital to halt the wave of sectarian killings.

In Washington, Prime Minister Nouri al-Maliki told Congress that Iraq was a front line in the war on terrorism and said those behind the violence here are perverting Islam.

The arrests occurred when troops of the 101st Airborne Division swept through a neighborhood in Mahmoudiya, 30 kilometers (20 miles) south of Baghdad, a U.S. statement said. The five included the team leader, the statement said.

Tensions have been running high in Mahmoudiya since July 17 when dozens of suspected Sunni gunmen killed at 50 people and wounded more than 90, most of the Shiites.

Four days later, Iraqi soldiers backed by a U.S. helicopter killed five gunmen in what U.S. officials said was a move against death squads. Six Iraqi security troopers were also killed.

The U.S. statement did not say whether the death squad members were Sunnis or Shiites. Shiite militiamen of the Mahdi Army and Sunni insurgents from Al Qaeda in Iraq-affiliated groups operate in the religiously mixed city.

A steady rise in violence since al-Maliki's government took office May 20 has drawn new attention on sectarian militias and death squads, whose tit-for-tat killings have raised fears that the country may be unraveling.

Much of the violence has occurred in greater Baghdad in what U.S. officials have described as a "must-win" battle between militants and the new government for the future of Iraq. The U.S. military plans to move American and Iraq from other areas in the country to keep the capital from descending into chaos.

In Washington, al-Maliki told a joint session of Congress that his government was committed to defeating its adversaries and abolishing the sectarian militias responsible for fueling the violence.

"I know some of you question whether Iraq is part of the war on terror," al-Maliki said. "Let me be very clear. This is a battle between true Islam, for which a person's liberty and rights constitute essential cornerstones, and terrorism, which wraps itself in a fake Islamic cloak."

Meanwhile, several bombings and shootings were reported in Baghdad and elsewhere, although the violence appeared lower than last week.

A car bomb injured 15 people in the northern oil center of Kirkuk, police said. It was the fifth car bomb in Kirkuk this month as tensions among the city's Arabs, Kurds and Turkomen are rising.

A roadside bomb exploded on an Iraqi army patrol near Karmah, 40 kilometers (25 miles) west of Baghdad, killing four soldiers, police Lt. Ahmed Ali said.

Two brothers serving in Iraq's police force died when a bomb blew up their vehicle as the two were traveling to the Baghdad suburb of Nahrawan, police Lt. Bilal Ali Majid said.

Gunmen abducted a senior Interior Ministry official, Gen. Abdullah Hmoud, as he rode in an unmarked car in Baghdad, police said.

A senior officer in the police unit that protects oil installations was slain in west Baghdad, police reported.

Police found two unidentified bodies of men in their 20s in the Baladiyat area eastern Baghdad. Both were blindfolded and shot in the head, police Capt. Haidar Ibrahim said.

In Kut, officials said about 2,480 families — or 14,900 people — have fled three religiously mixed neighborhoods in Baghdad in recent weeks for Wasit province, a mostly Shiite area southeast of the capital.

The province has long served as a refuge for Shiites in Baghdad who feel threatened by sectarian violence.