Mortar attacks on a camp housing Iranian dissidents near Baghdad killed a number of people early on Saturday, an Iraqi security official and a United Nations spokeswoman said.
The mortars "led to a number of deaths and injuries among the residents," said Eliana Nabaa, spokeswoman for the UN mission in Iraq. "Also a number of Iraqi policemen were injured... We cannot confirm exactly how many."
An interior ministry official, speaking on condition of anonymity, put the toll at five dead and 40 wounded from around 40 rocket and mortar attacks.
The Mujahedeen-e-Khalq (MEK) said in a statement that six people were killed by 35 rockets and mortars.
Nabaa said UN special envoy Martin Kobler had asked Iraqi authorities to "promptly conduct an investigation into this," and added, "we have our monitors on the ground to follow-up."
She said Iraqi officials had said that "all those who were injured were hospitalised immediately."
The mortars struck at a transit camp known as Camp Liberty where some 3,000 residents from the MEK were moved last year on Iraq's insistence, from their historic paramilitary camp of the 1980s -- Camp Ashraf.
The United States once regarded the MEK as a "terrorist group" but removed the cult-like leftwing group from its blacklist in September.
The Mujahedeen-e-Khalq 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.