BAGHDAD  —  Iraqi forces raided a camp housing members of an Iranian opposition group north of Baghdad on Tuesday in a move that ran contrary to U.S. wishes and prompted clashes.

Residents of Camp Ashraf claimed the Iraqi troops opened fire and beat people with batons, killing four people. The Iraqi government confirmed authorities had moved into the camp but denied violence was used against the exiles.

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The action sharply escalated tensions that have been on the rise since the U.S. military turned over responsibility for the camp to the Iraqis as part of a security pact on Jan. 1.

Iraq's government has stepped up pressure to get the People's Mujahedeen Organization of Iran to leave the country as it seeks to protect its friendly relations with Tehran. But it has not decided how to oust the exiles, and the United States insists they should be treated humanely and not be forcibly deported to a country where they could face persecution.

The group is considered a terrorist organization by the United States, although it has provided the Americans with intelligence on Iran.

The standoff reflects the delicate task the Iraqis face in balancing ties between the U.S. and Iran, and Tuesday's incident could be an embarrassment to the United States since it coincided with a visit to Baghdad by Defense Secretary Robert Gates.

The top U.S. general in Iraq said the raid followed a dispute over whether Iraq could establish a police station inside the camp, which is located north of Baghdad in Diyala province. Iraqi forces entered the camp "using non-lethal force" to set up the police station without the consent of the People's Mujahedeen, according to Gen. Ray Odierno.

The Iraqi government did not inform the United States in advance of its plans to raid Camp Ashraf, he added.

"We have had promises from the government of Iraq that they would deal with the MEK in a humane fashion," Odierno said, using the group's Farsi initials. "Using non-lethal force is a good sign."

However, a video provided by the People's Mujahedeen showed Iraqi forces using batons and water cannons against the residents gathered at the camp's gates. The group also released photos showing injured people and bloodied bodies, although the authenticity of the images, which also were circulated on YouTube, couldn't be independently verified.

Access to the camp, which is located in a dangerous area, is strictly controlled, making it difficult to independently confirm what happened Tuesday.

Government officials struck a hard line, saying they had a right to enter the camp and set up the police station as part of new measures to establish security. Ali al-Dabbagh denied the troops were violent with the residents.

"We do not intend the worse for them and we will not force them to depart against their wishes, but they should cooperate with the governmental procedures," he said.

Defense Ministry spokesman Maj. Gen. Mohammad al-Askari said Iraq had a sovereign right to enter the camp.

"They are on Iraqi territory, therefore it is not a storming of the area but entering Iraqi land as is our right," he said on Al-Arabiyah television.

Some 3,500 people are thought to live in the camp, about 80 miles (130 kilometers) north of Baghdad.

The raid came a day after the Iraqi government, which has maintained a security cordon around the camp's perimeter, said it would assume complete control of the camp but promised to protect the people inside.

That raised fears the Iraqis would move to forcibly evict the exiles, and the group's leaders announced shortly afterward that they were willing to return to Iran if they were guaranteed immunity from prosecution. They insisted on guarantees in writing from Iran, the United States, the United Nations and Iraq.

Officials with the People's Mujahedeen claimed that some 300 people were wounded and four people were killed. They identified those killed as Mehrdad Niksiar, Mohammad Reza Bakhtiari, Hamid Sarzin Zamani and Mehrdad Rezazadeh.

Maryam Rajavi, the president-elect of the National Council of Resistance of Iran — an umbrella group that includes the People's Mujahedeen — claimed American troops witnessed the event but did not intervene except to take pictures.

"We ask President Obama to intervene," she said. "It is the responsibility of the United States government of President Obama in particular to end this catastrophe."

The U.S. State Department reiterated Tuesday the Iraqi government has assured it that no member of the group in Iraq will be forcibly transferred to a country where they fear persecution.

"We continue to monitor the situation closely to ensure the residents of Camp Ashraf are treated in accordance with Iraq's written assurances that it will treat the residents there humanely," State Department spokesman Ian Kelly said in Washington. "This is really a matter for the government of Iraq to handle. This is completely within their purview. But we are closely monitoring it."

Iran has pressed for years to close the camp, but the issue came to a head after Iraqi forces took over security for the base.

Saddam Hussein allowed the Iranian exiles to establish their base in Diyala in 1986 to launch raids into Iran during the two neighbors' eight-year war. At the same time, many Iraqi Shiites fled to Shiite-dominated Iran and some of them fought on the Iranian side against Iraq.

U.S. troops disarmed the Iranian fighters and confined them to Camp Ashraf after the 2003 invasion of Iraq. The U.S. military in Iraq later signed an agreement with the militia, promising members would be treated as "protected persons" under the Fourth Geneva Convention.

Founded by Iranian leftists, the group opposed Iran's U.S.-backed Shah Mohammad Reza Pahlavi and took part in the 1979 revolution that brought a clerical regime to power, but its blend of Marxism and secular Islamism eventually pitted it against the mullahs in Iran.

Many of camp Ashraf's residents have citizenship in a Western country, including some in the United States.

The European Parliament urged Iraq in April not to deport members of the group, which was removed from the European Union's terror list earlier this year, to Iran because they face possible abuse or torture in Iran.