Abkhazia said today it has launched an operation to drive Georgia out of a disputed gorge, possibly opening a "second front" in Tbilisi's battle to retain fractious breakaway regions.

The separatist foreign minister Sergei Shamba said Abkhazian artillery and warplanes struck Georgian forces in Kodori, a narrow gorge which cuts deep into the Abkhazian territory and is an ideal route for any invasion in the region.

The attack came less than 48 hours after Georgia sent troops to retake the breakaway province of South Ossetia, triggering an invasion of Russian forces dispatched to restore the status quo.

"Abkhazian forces, in response to the Georgian aggression against South Ossetia, have started a military operation the Kodori gorge to clear it from illegal Georgian troops," Minister Shamba told Reuters.

Minister Shamba said at 9 a.m. Abkhaz warplanes launched airstrikes at the Tbilisi-controlled upper part of the Gorge and artillery was pounding the area.

"Today was only the initial part of the operation by heavy artillery supported by aviation," Minister Shamba said.

Georgians denied an all-out Abkhaz attack and said they were ready to face down any aggression.

"Rebels in Abkhazia have not attacked the Georgian forces," Kakha Lomaia, secretary of Georgia's Security Council, said.

"We have enough forces to react properly and defend ourselves in Kodori."

Abkhazia and South Ossetia, which are backed by Russia, broke away from Georgia after bloody wars in early 1990s and say they will take nothing less than full independence. Georgia sees their return as a top national priority.

South Ossetian and Abkhaz leaders have pledged to help each other in opposing Georgia.

After Georgia sent troops to South Ossetia, Abkhazia pulled its own forces closer to the Georgian border and sent more than 1,000 volunteers to the embattled province.

The separatist leaders have suspected Georgia's pro-Western President Mikheil Saakashvili of planning to seize the provinces back by force. Saakashvili has pledged to find a peaceful way of re-integration.

The Abkhaz separatists have accused Georgia of building up security forces in the upper part of the Kodori gorge, a demilitarised zone under agreements which ended the previous war in 1994.

Tbilisi denied any military build-up in the sensitive area, but made the upper part of the gorge a seat for a loyal Abkhaz government in exile.

A spokesman for pro-Tbilisi government said Russians, rather than Abkhazians, bombed the gorge.

"Earlier today... Russian jet fighters bombed two villages in the upper part of the gorge," Raul Kiria told Reuters by telephone.