The headquarters of the Badr Organization, Iraq's most feared Shiite Muslim militia, sits behind blast walls and armed checkpoints in a cluster of large homes near a highway overpass in the Baghdad neighborhood of Jadriyah.

Less than a mile away in the same wealthy district stands the Interior Ministry prison where two weeks ago U.S. soldiers found 173 inmates, many of them malnourished and showing signs of torture; most of them were Sunni Arabs.

Sunni Arab leaders immediately blamed the Badr Organization, many of whose members have joined the Iraqi security forces. The militia's claim to have abandoned arms for politics is widely disputed by U.S. officials and Iraqis outside Shiite leadership.

But in an interview conducted over tea in a spartan home with a verdant garden, Haidi Amery, head of the militia -- an affiliate of the Supreme Council for the Islamic Revolution in Iraq, the dominant party in Iraq's government -- denied that the group was involved with the prison. At the same time, Amery, wearing a suit with no tie, dismissed criticism of the methods used there as hypocritical, citing the mistreatment of detainees by Americans and Iraqis at other facilities.

He also argued that U.S. soldiers carried out the Nov. 13 raid to draw attention from intensifying calls for the withdrawal of American troops from Iraq.

"When an American soldier shoots someone in the street, they say it's his right because the situation is tense," said Amery, adding that his organization was opposed to torture. "We accept that U.S. soldiers kill in suspicion and fear, and we should keep in mind also the tension of police and soldiers."

He also said that U.S. commanders had long been aware of the Interior Ministry prison facility, where in recent days inmates have described how prisoners were tortured with electric shocks and killed by having their skin peeled from their bodies.

"The Americans called it a secret facility, but they were lying. They knew about it. They had been there several times. They had even assigned $1 million to rehabilitate it. If there was torture, I doubt they did not know about it," he said. "Do you think the Americans don't allow torture? What about what happens at Abu Ghraib? What about Camp Bucca?" he said, referring to two of the U.S. prison facilities in Iraq where detainee abuses have been documented.

A spokesman for the U.S. Army's 3rd Infantry Division, which conducted the raid after receiving a tip about a missing teenager, did not immediately respond to a telephone call seeking comment on Amery's charges. Those charges could not be verified.

The militia leader's remarks came amid increasing scrutiny of the group. Sunni political leaders see its hand in nearly every crime committed against their people and blame the group for the prison abuses. Government investigators were due to present their findings about the prison on Wednesday, but missed their deadline.

Amery claimed the November raid was timed by the United States to disrupt a conference in Cairo aimed at reconciling differences among Iraq's Shiite, Sunni Arab and Kurdish factions. The conference concluded Nov. 21 with a joint statement calling on the United States to produce a timetable for withdrawal.

Militias in Iraq were officially outlawed under Order 91, a law passed by the U.S.-led Coalitional Provisional Authority that ran the country in the year following the 2003 invasion. At the time, militia members were encouraged to join Iraq's nascent security forces. Many of them did, and the group is now deeply enmeshed with Iraq's police and army.

Amery said that Badr has become a broader political organization, with hundreds of thousands of supporters and more than 10,000 registered members, but only about 1,000 men under arms. The armed members' role is to protect the organization's offices across the country, he said.

"We aim to exercise power through the political process and we have given away our weapons in full confidence," he said. "We reject the term militia."

Beyond its link with the Supreme Council, which boasts more seats than any other party in Iraq's National Assembly, Badr's political clout is most evident at the provincial level. A third of Iraq's provincial governors are members, including Baghdad's, Amery said.

As sectarian violence escalated across Iraq in recent months, the Association of Muslim Scholars, a Sunni Arab religious group, has accused the Badr Organization of torturing and executing Sunni political and religious figures, and has posted graphic images of bruised and battered bodies on its Web site.

In Sunni-dominated regions of Iraq, the Badr group is blamed for virtually every violent crime, leading to deep distrust of Iraq's security forces. Founded to fight the Sunni-led government of former president Saddam Hussein, the Shiite militia largely operated from exile in Iran until the U.S. invasion.

"We think the interior and defense ministries are infiltrated by these people. Badr is turning the life of the Iraqis in general into a hell," said Ahmed Ali, 55, who owns a small market in the predominantly Sunni Baghdad neighborhood of Adhimiya. "It's all Badr troops. They hate Iraqis because they became Iranians. Iran is trying to destroy the country by them. They think that they are getting revenge on us."

Many U.S. soldiers say they distrust the Iraqi police, who unlike the Iraqi army operate largely independently of American forces. On a foot patrol near Baghdad's Haifa Street one recent evening, American soldiers accompanying an Iraqi army platoon came upon a half-dozen Iraqi police officers and a pair of blue and white vehicles forming a makeshift checkpoint in the street.

"I want an ID check on every one of those guys," said Lt. Lennie Fort, 30, of Clarksville, Tenn. "Ask them who they are and what they are doing here."

The officers were made to get out of their vehicles while Iraqi soldiers examined their identification cards for forgeries and questioned them. Their story checked out: policemen in one car said they were investigating a report of suspicious vehicles driving through the area. The other car belonged to a supervisor who had stopped by to make sure his men had not fallen asleep.

A Western diplomat in Baghdad said in a recent briefing for reporters that militias, operating within the purview of Iraq's security forces "have been involved in extrajudicial killings as well as things like kidnappings."

In one high-profile example, in October, armed men in uniforms burst into the home of Iraqi attorney Sadoun Janabi, who represented one of Hussein's co-defendants. He was found dead a day later.

"This is a very serious and dangerous situation," said Hussain Ali Kamal, undersecretary for intelligence of the Iraqi Interior Ministry. "We still don't know who these people are and we're investigating to try to find them. They use police cars, police uniforms, flak jackets and police weapons."

Asked about claims of mass killings by militias, Amery denied them.

"We could make accusations," he said. "But we don't want a civil war."

Staff writer Jackie Spinner and special correspondents Omar Fekeiki and Bassam Sebti contributed to this report.

Adnan Rawi of the Association of Muslim Scholars, a Sunni group, displays photos of a man he said died after being tortured in an Interior Ministry prison. Sunnis accuse the main Shiite militia, the Badr Organization, of orchestrating detainee abuses, including torture at the prison.