PRISTINA, Yugoslavia (AP) _ A large explosion damaged a Serbian Orthodox Church under construction in the heart of Kosovo's capital early Sunday, the latest sign of ethnic hatred threatening the province's fragile stability.

The blast came just hours after British Prime Minister Tony Blair visited Pristina, urging peace and trust on all sides.

Tensions over the presence of Russian peacekeepers in Kosovo also have risen sharply after the Russians on Saturday briefly detained a top commander of the Kosovo Liberation Army, chief of staff Agim Ceku, drawing an angry warning from the KLA.

If such actions aren't stopped, ethnic Albanian rebel leader Hashim Thaci warned, ``We will defend our honor.''

The church blast came against a backdrop of frequent attacks on minority Serbs in Kosovo, where violence has continued despite the presence of more than 35,000 NATO troops. Ethnic Albanians in Kosovo have been seeking revenge for forced removals, house burnings and killings at the hands of Serbs, which prompted NATO's 78-day bombing campaign this spring.

No one was reported injured in the explosion at the Sveti Spasa church, which had not yet opened. The blast was heard throughout Pristina, setting off car alarms and sending a large cloud of smoke and dust into the air.

British explosives experts were at the site later Sunday morning, some four blocks from the site of the KFOR peacekeeping force's headquarters.

Capt. Tony Tesar told Associated Press Television News that damage to the church was minimal. He said that six five-pound charges were found inside, but that not all of them had been detonated. He said the perpetrators used a timing device that allowed them to leave the scene before the blast.

Capt. Stefan Eder, a KFOR spokesman, said officials did not know who was behind the blast.

Barely 12 hours before the explosion, Blair had reportedly assured Kosovo Serb representatives pleading for protection that KFOR would do its best to ensure the safety of all sides.

Momcilo Trajkovic said he had an ``open and direct'' discussion with Blair, to whom ``we conveyed the protest of the Serb community, which is now in a catastrophic situation.''

``Unless the murders, rapes, looting and burning do not stop soon, all his pledges for a multiethnic Kosovo will come to nothing,'' Trajkovic said he told the British premier.

Blair received a hero's welcome from ethnic Albanians who cheered his appearance in Pristina on Saturday. He was the third top Western official in the last 10 days to visit Kosovo, following German Chancellor Gerhard Schroeder and U.S. Secretary of State Madeleine Albright.

The flap over the detention of Ceku was the latest indication of the animosity many ethnic Albanians harbor toward the Russians.

The KLA and others distrust the Russians as staunch Serb allies, saying some fought alongside Serb forces during the brutal campaign against the province's Albanian majority.

Ceku, who confers regularly with the NATO-led peacekeeping force over the KLA's progress toward meeting a disarmament pledge, was stopped on Saturday in an area of western Kosovo where Russian troops conduct patrols inside the German-controlled sector.

A spokesman for the international peacekeepers played down the incident, saying Ceku apparently was questioned because he was traveling with four armed bodyguards and wasn't carrying the card authorizing him to do so. Lt. Cmdr. Louis Garneau said the detention lasted no more than an hour.

But Thaci, who claimed it lasted several hours, summoned reporters to complain that it confirmed rebel doubts about Russian participation in the peacekeeping force.

He demanded that British Lt. Gen. Mike Jackson, the head of the peacekeeping force, ``control'' Russian troops and ensure they don't ``insult the KLA.''