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

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

Mr. 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 Georgian breakaway 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 on 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. However, 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 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.