Peacekeepers scrambled to keep a lid on simmering ethnic tensions today after a bomb damaged a Serbian Orthodox church under construction in Kosovo's capital.

The early morning blast did little damage to the structure, but it further undermined the confidence of minority Serbs in the ability of Western peacekeepers to protect them from violence that they say is committed by ethnic Albanians.

The bombing "was not a surprise, because for the last few days we have been telling every day the [peacekeeping] officers that this is going to be the next target," said the Rev. Sava Janjic, a prominent Serbian Orthodox priest in Kosovo. "We very much wonder why it couldn't be prevented."

No one was reported injured in the explosion, which was heard throughout the capital, setting off car alarms and sending a large cloud of smoke and dust into the air.

British Capt. Tony Tesar said damage to the church, which had not yet opened, was minimal. He said six five-pound charges were found inside the structure, but not all of them had been detonated. He said the perpetrators used a timer.

NATO issued a statement saying it "vigorously condemns this cowardly attack against a place of worship" and was carrying out an investigation.

The bombing added to tensions already running high after Russian peacekeepers briefly detained the Kosovo Liberation Army's military commander, Agim Ceku. In response to the detention Saturday, ethnic Albanian rebel leader Hashim Thaqi warned that if such actions are not stopped, "we will defend our honor."

Russia defended the action of its peacekeepers and accused the rebel group of flouting the peace process.

The statement called Thaqi's response "a crude provocation" and criticized what it termed "the impunity of the KLA, which is carrying out illegal violence against local Serbs."