A U.N. team headed to a camp housing Iranian exiles north of Baghdad on Monday after residents alleged soldiers killed dozens of their members, charges Iraqi officials strongly denied.
Iraqi Prime Minister Nuri al-Maliki, meanwhile, set up his own investigation into the unrest to sift through wildly differing accounts of Sunday's events, in which clashes and explosions were reported but the extent and causes of the casualties remained in doubt.
The People's Mujahedeen Organisation of Iran (PMOI) said on Sunday that Iraqi forces killed 52 of their members at Camp Ashraf, the group's long-time base in Diyala province near the Iranian border, and set fire to their property.
But Iraqi officials insisted no soldiers entered Ashraf, and said explosions were triggered by mortar fire or the explosion of a barrel of oil or gas.
"There was a mission that went (to Ashraf) a little bit earlier to see what they can do there," Eliana Nabaa, spokeswoman for the U.N.'s mission in Iraq, told AFP.
"They will try to determine the facts."
Maliki's committee began its investigation late on Sunday, according to the prime minister's spokesman Ali Mussawi, and was expected to report back in the coming days.
The violence was condemned by the U.N.'s refugee agency, which is charged with relocating the group's members outside of Iraq, and the U.S. State Department, but neither assigned blame for the unrest.
It follows two mortar attacks earlier this year on another camp housing the group, also known as the Mujahedeen-e-Khalq (MEK), in which at least eight people were killed.
Officials and MEK spokespeople gave totally different accounts of Sunday's unrest and it was not immediately clear what caused the explosions and clashes, or the extent of the casualties.
Iraqi officials said mortars hit the camp, and Ashraf residents subsequently attacked a nearby army brigade, killing three soldiers and wounding four.
They said that no troops entered Ashraf, and the blasts in the camp were likely caused by barrels of oil and gas exploding.
The MEK, however, charged Iraqi forces with carrying out a "massacre" and the group's members at another camp near Baghdad began a hunger strike on Monday, a spokesman said.
Around 3,000 MEK members were moved from Ashraf to Camp Liberty, located on a former U.S. military base on the outskirts of Baghdad, last year, but about 100 stayed on at the old camp in order to deal with leftover property and goods.
Former Iraqi dictator Saddam Hussein allowed the rebel MEK to set up the camp during his war with Iran in the 1980s.
The MEK was founded in the 1960s to oppose the shah of Iran, and after the 1979 Islamic revolution that ousted him it took up arms against Iran's clerical rulers.
It says it has now laid down its arms and is working to overthrow the Islamic regime in Iran by peaceful means.