MOSCOW - A Russian fighter jet shot down an unmanned Georgian spy plane over the separatist Abkhazia region last month, U.N. observers said yesterday in a report likely to bolster U.S.-allied Georgia's claim that the Kremlin is undermining its territorial integrity.

In recent months, the government of Georgian President Mikhail Saakashvili has used drones to monitor Abkhazia and the peacekeeping force that Russia has reinforced there. Russian officials denied again yesterday that they had anything to do with the aircraft's being shot down.

Saakashvili's efforts to move the former Soviet republic from under Russia's shadow and into NATO and the European Union have angered Moscow, which is supporting local leaders in Abkhazia and another breakaway Georgian area, South Ossetia.

The West's interest in the dispute is strong because Georgia sits at the crossroads for Central Asian and Caspian Sea oil and natural gas headed to Western markets.

The Georgian drone was shot down April 20, and a video it transmitted before being destroyed shows a fighter jet firing a missile at it.

The region's separatist government claimed one of its L-39 jets was responsible. But the video showed the jet that fired the missile had a distinctive twin-finned tail, while L-39s have single-fin tails.

The United Nations mission, which has been in Georgia since just after Abkhazia and South Ossetia broke away from the central government's control in the early 1990s, concluded yesterday that the fighter jet was either a Russian-made MiG-29 or a Su-27, neither of which Abkhazia has.

Radar tracking shows that after the drone was shot down, the fighter jet headed into Russian airspace, the report said. "Absent compelling evidence, this leads to the conclusion that the aircraft belonged to the Russian air force," it said.

A Russian Defense Ministry spokesman disputed the U.N. finding. "There cannot be any talk of any kind of violation of the state border of Georgia or of the shooting down of an unpiloted flying apparatus," Col. Alexander Drobyshevsky said in televised comments.

The U.N. report said Moscow's actions were "fundamentally inconsistent" with the 1994 cease-fire agreement that authorized a Russian peacekeeping force and separated Georgian and Abkhazian forces.

After the report's release, the European Union said Russia must explain its actions, and EU foreign policy chief Javier Solana said he would travel to Georgia next week.

Russia, which has about 2,500 soldiers in Abkhazia, does not formally recognize Abkhazia's or South Ossetia's governments, but it maintains close contact with them and has granted passports to most residents of the two regions. Last month, Russia called for upgrading its ties with Abkhazia, a move that angered Georgia.

The U.N. report came as up to 50,000 people marched in Georgia's capital, Tbilisi, to protest results showing that Saakashvili's party won a big victory in last week's parliamentary elections.

Saakashvili had hoped to burnish his democratic credentials and seek membership in NATO and the EU to help his poor country. But the opposition refused to accept the results, accusing authorities of widespread violations. The United Opposition alliance won just 16 seats in the 150-seat assembly; the president's party won 120 seats.

The march was one of the biggest showings of discontent since a November crackdown on opponents tarnished Saakashvili's image as a reformer.