The UN concluded in a report Monday that a Russian fighter jet shot down an unmanned Georgian spy plane last month, prompting the EU to call on Moscow and Tbilisi to "explain themselves."

The report, posted on the UN website, said evidence gathered by UN monitors "leads to the conclusion that the aircraft belonged to the Russian air force" and that the downing was "fundamentally inconsistent" with ceasefire accords.

Russia's defence ministry rejected the findings, with spokesman Alexander Drobyshevsky telling AFP: "We deny this report. Our planes did not violate anyone's airspace and therefore could not have fired a shot."

The incident is one of the most serious in the volatile region since the end of a military conflict in 1993 between Georgian troops and Moscow-backed separatist rebels in the Georgian breakaway province of Abkhazia.

The European Union's Slovenian presidency said the UN report was "balanced" because it criticised Russia as well as Georgia for deploying the spy plane in the area in violation of a ceasefire agreement.

"It's a balanced report," Slovenian Foreign Minister Dimitrij Rupel told reporters in Brussels after chairing a meeting of his EU counterparts.

"We think that those who have been found responsible should explain themselves," Rupel said.

Georgian President Mikheil Saakashvili said the report vindicated Tbilisi's claims that the Russian military has been violating its sovereignty.

"Georgia today is in a very difficult situation because foreign armed forces have entered its territory," he said in televised remarks.

"The UN has released a report in which Russia is directly accused of aggression against Georgia.... For the first time, the UN has directly, unequivocally pointed the finger at Russia."

Russia, which backs the Abkhaz rebels in the lush Black Sea province, has denied violating Georgian airspace and says that Abkhaz forces shot down the Georgian drone on April 20 -- a claim supported by Abkhaz officials.

But the report, obtained by AFP ahead of its release by the UN, stated that a MiG-29 or Su-27 warplane was used in the incident and that the aircraft then "turned back north heading... into Russian airspace."

The text was highly critical of the drone shooting, saying it violated a ceasefire agreement between Georgian forces and Abkhaz rebels -- and called into question the separation of Russian peacekeepers from the conflict.

The UN mission "considers that enforcement action by third parties -- in this case the Russian Federation -- is fundamentally inconsistent with the Moscow agreement and, aside from possible considerations under international law, undercuts the ceasefire and separation of forces regime," the report said.

The report also indicated that the incident may have posed a threat to civilian aircraft.

"The interception took place very close to, or even inside, an international airway at a time (when) civilian aircraft were flying," it said.

Analysts said the report could give a major boost to Georgian efforts to replace Russian peacekeepers in Abkhazia, whom Tbilisi accuses of siding with the rebels, with an international force.

"This is going to have a huge impact," said Tornike Sharashenidze, a Tbilisi-based analyst.

"Now Georgia has a report from a neutral body on the Russian militarisation of Abkhazia. Georgia will be able to count on much stronger support, not only from America, but from Europe," he said.

The text said its conclusions were based on analysis of witness statements, radar records and video taken by the Georgian drone that filmed itself under attack at close range by a warplane.

The drone footage had not been doctored in any way, the UN report said.

Tense relations between Russia and Georgia, whose pro-Western leadership is pushing for entry into NATO, have flared up repeatedly over the last month in Abkhazia.

Georgian officials warned that the two countries had come close to war and Russia announced it was sending reinforcements to a Russian troop contingent deployed in Abkhazia as peacekeepers.

But Russian President Dmitry Medvedev appeared to strike a more conciliatory tone on Monday in a message to Saakashvili congratulating him on Georgia's independence day.

Medvedev said he hoped for "constructive" cooperation with Georgia, promoting "good neighbourly relations" and "fostering stability and security in the Caucasus," the Kremlin said in a statement.