The United Nations and Nato have been accused of failing in their duty to protect the minority victims of ethnic clashes in Kosovo earlier this year.
Peacekeepers are accused of standing by as Kosovo burned
Pressure group Human Rights Watch also accused the international community of being in denial over its failure.
The UN and Nato have rebuffed the report and defended their role.
Nineteen people were killed and hundreds of homes were torched in violence between ethnic Albanians and the UN-administered province's Serb minority in March.
The Human Rights Watch report said the province's UN mission, which operates a 3,500-strong police force, and its 18,000 Nato-backed peacekeepers had not co-ordinated their response to the violence which swept the province.
"In many cases, minorities under attack were left entirely unprotected and at the mercy of the rioters," it said, adding that local police were ill-equipped to deal with the rioting.
The report called for more international troops and police personnel to be deployed in the province to contain future outbursts.
It also demanded the reform of "international security structures" and for the province's diverse foreign forces to be brought under a clearer, unified command.
"In too many cases, Nato peacekeepers locked the gates to their bases and watched as Serb homes burned," Rachel Denber from Human Rights Watch's Europe and Central Asia division said.
The report cited several instances of mobs attacking Serb property within close proximity of peacekeepers' bases.
But a spokesman for Kosovo's Nato forces, Col Horst Pieper, told the Associated Press news agency the pressure group had ignored the realities on the ground.
"These reports coming from [an] armchair position do not pay any respect to the efforts of the soldiers," who, he said, "quickly stabilised the situation".
The UN mission in Kosovo said the report did not appreciate the challenge that the violence had posed to the peacekeepers and police.
Hundreds of people, most of them Serbs, are still homeless after the riots, which swept through Kosovo over two days in March this year.
Investigations into the origins of the violence have blamed local media for stoking inter-ethnic tensions.
It was the worst violence Kosovo had seen since 1999, when a Nato bombing campaign ended a Serb crackdown in the mainly ethnic-Albanian province.
Though governed by the UN, the province is formally still under Belgrade's rule and its final status has yet to be resolved.