At least 15 people have been killed and 50 wounded in clashes after a mortar attack on an Iranian dissident camp north of the Iraqi capital Baghdad, two security sources told the Reuters news agency.
Iraqi security forces opened fire on a crowd which had stormed a post at the entrance to Camp Ashraf, a site that Iraq's government wants closed down, a source said.
The Mujahadin-e-Khalq (MEK) dissident group said 44 of its roughly 100 members in the camp had been killed by Iraqi security forces.
Some of them were shot with machine-guns with their hands tied behind their backs, MEK said in a statement.
Around 3,000 MEK members were moved from Ashraf to Camp Liberty, located on a former US military base on the outskirts of Baghdad, by September 2012.
But about 100 stayed on at the old camp in order to deal with leftover property and goods.
The United Nations in Iraq strongly condemned Sunday's "tragic events", without giving details on what had happened.
MEK called for the overthrow of Iran’s clerical leaders and fought alongside the forces of former Iraqi Sunni Muslim ruler Saddam Hussein in the Iran-Iraq war in the 1980s.
The group was forced into exile in 1981 after the Iranian revolution, according to the Council on Foreign Relations.
It has been trying to recast itself as an Iranian opposition force but is no longer welcome in Iraq under the Shi'ite Muslim-led government that came to power after US-led forces invaded the country and toppled Hussein in 2003.