The United States and Russia are holding military exercises on either side of the Caucasus mountains amid increasing tensions over the fate of two separatist regions in ex-Soviet Georgia.

Almost 8,000 Russian servicemen began anti-terrorism exercises on Tuesday across Russia's north Caucasus region, which borders Georgia, a spokesman for the Russian army said.

In Georgia itself, a total of around 1,650 soldiers form the US, Georgia and several other East European countries, have begun exercises on the formerly Russian-controlled Vaziani base, the Georgian defence ministry said.

Tensions between Georgia and Russia have soared in recent months as Moscow has increased its support for Georgia's separatist regions of Abkhazia and South Ossetia.

The Russian exercises were planned a year ago and "are in no way related to the US-Georgian activities," Igor Konashenkov, a Russian army spokesman said.

Russian 'peacekeeping'

Moscow has also been angered by Georgia's moves to join the Nato.

Nana Intskirveli, a spokeswoman for the Georgian defence ministry, said the exercises were taking part under the auspices of the military alliance.

She said Armenian, Azerbaijani and Ukrainian staff officers were are also taking part in the exercises, which will last for three weeks.

Konashenkov said the Russian exercises were in part designed to prepare forces for peacekeeping work in Abkhazia and South Ossetia.

"In connection with the aggravated situation of the Georgian-Abkhazian and Georgian-Ossetian conflicts... we will also work on participation in special operations to bring peace to zones of armed conflicts," he said.

Around 700 pieces of military hardware will be used during the exercises, he said.