Three ethnic Tamil rebels blew up their boat and themselves today after they were found trying to smuggle an antiaircraft gun and hundreds of rounds of ammunition into Sri Lanka, defense officials said.

Two European peace monitors who had boarded the boat to inspect it were unharmed. Before blowing up their boat, the rebels asked the monitors to jump overboard, a military spokesman, Brig. Sanath Karunaratne, said in a statement.

The monitors, who searched the trawler this morning, found an antiaircraft gun, spare parts for the gun, two boxes of ammunition, three hand grenades and a radio communication set, Karunaratne said.

The monitors had earlier said the find was a "clear violation" of a cease-fire agreement the rebel Liberation Tigers of Tamil Eelam signed with the government last February. The Tigers began fighting in 1983 to create a separate state for Sri Lanka's minority Tamils. The war has killed nearly 65,000 people and displaced more than 1.6 million.

The rebels dropped a demand for a separate state last year and agreed to discuss setting up a federal system that would give them regional autonomy.

The explosion came only hours before a fifth round of peace talks started in Berlin. Norwegian mediators drafted a statement to keep the negotiations on track, blaming the explosion on an "apparent communication failure" between the rebels and their commanders.

Sri Lanka's government has repeatedly accused the rebels of smuggling arms during the cease-fire. There was no comment from the rebels.