"We can confirm that a helicopter was shot down by a missile," said Alexandra George, political affairs officer for the U.N. observer mission in Georgia.
Four U.N. observers, two local staff and three Ukrainian crew were on board the Mi-8 helicopter, the officials said. A rescue operation was under way, joined by U.N. personnel from Sukhumi, Abkhazia's capital.
At U.N. headquarters in New York, Secretary-General Kofi Annan expressed shock at the attack and members of the Security Council demanded that those responsible be quickly identified and brought to justice.
Council members, in a statement read to reporters, "recalled that it is the primary responsibility of both sides to provide appropriate security conditions for the work of the mission at all times."
The helicopter was on a regular twice-weekly U.N. observation flight to the Kodori gorge where Abkhaz officials say Georgian guerrillas and Chechen rebel groups are operating. However, it was unclear who shot the helicopter down or why.
The helicopter smashed into Sugar Head Mountain, 50 miles from Sukhumi. The Kodori gorge, located between Abkhazia and Georgia, is disputed territory between the two sides and a lawless area.
Members of the U.N. Observer Mission in Georgia, known for short as UNOMIG, are deployed on the separation line between Georgia and Abkhazia, which declared independence from Tbilisi in 1991.
An Abkhaz Defense Ministry spokeswoman said the U.N. team had gone ahead with the flight despite being warned at the weekend of the dangers posed by guerrillas.
"UNOMIG were warned Sunday by Abkhaz officials not to make their scheduled flight as it was a danger that their helicopter could be shot down, as a group of rebels are located in this area in the Kodori Gorge," said the spokeswoman.
Abkhaz servicemen near the crash site said they had heard the sound of a rocket being fired shortly before the helicopter exploded, she said.
Abkhazian separatists drove out Georgian forces in a 1992-93 war that ended in a cease-fire and de facto independence. Attempts to reach a political solution have failed, and the Black Sea province has remained plagued by clashes and bombings despite the presence of a Russian peacekeeping force.
In August, Georgian President Eduard Shevardnadze said he and Abkhazian Prime Minister Anri Dzhergeniya had made rare progress toward a political solution. Speaking four times in one long night, the two leaders managed to avert an attempted attack by Georgian rebels on Abkhazia. Shevardnadze said the planned attack had been fueled by discontent among ethnic Georgian refugees who were pushed out of their homes and see no hope for return.
Following Shevardnadze's intervention, Dzhergeniya said the Abkhaz side was ready to resume U.N.-brokred negotiations.
Georgia has denied Russian and Abkhazian allegations that it has allowed Chechen rebels to take refuge on its territory, though it has permitted refugees from the region's two wars to live there. Georgia is the only foreign country that borders on Chechnya.
Abkhazian authorities say a group of Chechen and Georgian rebels led by Chechen Ruslan Gelayev tried to take control of an Abkhazian village late last week. They say the militants were beaten back and they broke into small groups, which have taken refuge in the rugged Kodor gorge.
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