A rocket attack on a former U.S. military base near Baghdad has killed at least 20 exiled members of an Iranian opposition group who are seeking refugee status.
Several Iraqi security forces were also killed.
No one has claimed responsibility for the deadly barrage late Thursday against the People's Mujahedeen Organization, whose members fiercely oppose Iran's religious authorities.
They are staying at what has been dubbed Camp Hurriya, near Baghdad International Airport, while U.N. officials determine their refugee status and look for a permanent place for them to live.
Iraqi authorities say at least 15 rockets slammed into the camp.
U.S. Secretary of State John Kerry condemned the attack as brutal and senseless.
"No matter the circumstances, on this point we remain absolute: the United States remains committed to assisting the U.N. High Commissioner for Refugees in the relocation of all Camp Hurriya residents to a permanent and safe location outside Iraq."
The high commissioner calls the attack a "most deplorable act" and Secretary-General Ban Ki-moon reminded Iraq of its responsibility to provide for the safety of camp residents.
While the late Iraqi dictator Saddam Hussein welcomed the Iranian opposition members into Iraq, the current Baghdad government intensely dislikes the group and wants them out.