The United Nations confirmed Tuesday that its representative in Iraq's Diyala province, who had been missing since April, was murdered.
Amer al-Kaissy's body was discovered in November in the city of Baqubah, where the U.N. said he had been abducted by militias.
Local authorities buried the body without identifying it, and it was only Monday that al-Kaissy's friends identified the corpse through photographs.
Secretary-General Ban Ki-moon condemned what he called a "shocking murder" and called on Iraqi authorities to ensure that the killers are brought to justice.
The head of the U.N. mission in Iraq, Jan Kubis, said al-Kaissy's killing is a "brutal and cowardly crime." He also expressed disappointment in the failure of Iraqi authorities to locate al-Kaissy after the abduction.
"For more than nine months we have sought the intervention of the government on the local and national levels to ensure his safe return to his family," Kubis said in a statement. "We have expressed serious concern about the lack of progress in identifying his whereabouts and achieving his safe release. I am deeply disappointed that our efforts and appeals went unanswered."