The Iranian dissidents, the People's Mujahedeen, live in Camp Ashraf in northern Iraq near the Iranian border, said Iraqi security forces fired on camp residents Thursday into Friday, killing more than a dozen people, The New York Times reported.
In e-mails received by UPI, the People's Mujahedeen said 20 people had been killed and 300 injured.
"The Iraqi aggressing forces that started their murderous attack on Ashraf ... have removed the northern fences using a number of bulldozers and have entered the camp," an e-mail signed by the secretariat of the National Council of Resistance of Iran said, accusing Iraqi Prime Minister Nouri al-Maliki of authorizing the attack at the behest of Tehran.
"The oppressive forces are attacking the unarmed residents protesting the attack, using tear gas and water cannons and are throwing grenades at them."
The reports could not be independently confirmed, although U.S. officials expressed confidence in the information they received about the incident.
However, Gates told reporters in Mosul Friday U.S. officials were concerned.
"We're very concerned with reports of deaths and injuries resulting from this morning's clash," Gates said after talking to U.S. troops at Forward Operating Base Marez in Mosul. "I urge the Iraqi government to show restraint and live up to their commitments to treat residents of Ashraf in accordance with Iraqi law and their international obligations."
The camp houses several thousand Iranian dissidents who swore to overthrow the Iranian government.
Gates said no U.S. troops stationed near Camp Ashraf were involved in the clash, but may have offered medical assistance.