Iraqi forces took control of an Iranian exile camp north of Baghdad on Tuesday, the government said, in a move camp residents said triggered clashes killing four of the dissidents Iraq hopes to expel.
Iraqi government spokesman Ali al-Dabbagh could not immediately confirm or deny news of the deaths, but he had earlier said there had been no physical attacks when Iraqi security forces took control of the interior of the camp.
The Iraqi government has vowed to close Camp Ashraf, home to Iranian dissidents for two decades, and return members of the People's Mujahideen of Iran (PMOI) to Iran or a third country.
While Iraq and the United States deem the PMOI a terrorist group, the camp's 3,500 residents enjoyed some U.S. military protection after the 2003 invasion to oust Saddam Hussein, but Iraqi forces have gradually taken over.
"Four residents of Camp Ashraf, members of the PMOI, were shot and killed by the Iraqi security forces as a result of opening fire on the unarmed people in Ashraf at 8 p.m. today," Ashraf spokesman Shahriar Kia said in a statement.
Camp residents had started a hunger strike, he added.
Bezhad Saffari, an Ashraf resident and lawyer, had earlier told Reuters Iraqi forces fired tear gas at residents who barricaded a gate to try and prevent them entering the camp.
He said that many residents were wounded in clashes and that several others in the camp, where former leader Saddam gave refuge to opponents of the Iranian government, were arrested.
Dabbagh had earlier denied the attacks.
"From today, internal security at the camp is in the hands of Iraqis," he said.
US State Department spokesman Ian Kelly said the Iraqi government had assumed security responsibility for Camp Ashraf and that it was therefore up to Baghdad to handle the matter.
"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," Kelly told reporters in Washington.
PMOI footage sent to Reuters showed what seemed to be Iraqi security forces tussling with a rowdy crowd of demonstrators.
Iraq's Shi'ite-led government, which includes many former Saddam opponents who were exiled in Iran, has close ties to Tehran and is unsympathetic to the PMOI.
The group began as leftists against Iran's Shah but fell out with Shi'ite clerics who took power in the 1979 revolution.
The PMOI said in a statement that camp residents would be willing to go home if they had written assurances from Iran that any PMOI returning would "enjoy immunity from arrest, prosecution, torture, execution ... freedom of speech."
Iran is unlikely to comply, political analysts said.
While Iraqi officials insist they are respecting dissidents' rights, Ashraf residents accuse Iraqi forces of laying siege to it and sometimes blocking the entry of food and medicines.