Georgia's prime minister dismissed his ministers of defence and foreign affairs Friday in a major cabinet shakeup nearly four months after a disastrous war with Russia.

Prime Minister Grigol Mgaloblishvili told reporters that "new energy" was needed in the government as he announced the dismissals of Foreign Minister Eka Tkeshelashvili and Defence Minister David Kezerashvili as well as a radical shake-up of the diplomatic corps.

"We need to take significant steps in several directions to implement reforms, to fulfill promises and to further strengthen Georgian institutions and democracy," he said, according to a government statement.

"In the face of the threat to Georgia today... I believe that now is the time for new experience and new energy."

Culture Minister Grigol Vashadze, a longtime diplomat, will be named foreign minister and Deputy Defence Minister Batu Kutelia will be appointed to replace Kezerashvili, the prime minister said.

New culture and education ministers will also be appointed, he said.

Vashadze immediately announced a reshuffling in the foreign service, saying all deputy foreign ministers and ambassadors would be asked to resign.

"I am asking all deputy ministers and ambassadors to resign... Decisions on future appointments will be made according to the performance of these people during the war," he said in televised remarks after his appointment was announced.

Georgian President Mikheil Saakashvili was to make a televised statement regarding the changes later Friday.

The shakeup comes as Saakashvili faces increasing pressure for his handling of the war in August, which saw Russian troops pour into Georgia to repel a Georgian military attempt to retake the rebel region of South Ossetia.

Critics, including some former allies, have accused Saakashvili of provoking the war, which saw Russian forces occupy swathes of territory and bomb targets across the country, dealing a heavy blow to Georgia's economy.

Under a European Union-brokered ceasefire agreement, Russian forces later withdrew to within South Ossetia and another rebel region, Abkhazia, which Moscow recognised as independent states.

Saakashvili had earlier replaced his wartime prime minister with Mgaloblishvili but left most of the cabinet intact.

Tensions remain high around the rebel regions and on Friday Georgia's interior ministry accused South Ossetian rebels of shelling a Georgian police post near the breakaway province. No casualties were reported.

Russian Foreign Minister Sergei Lavrov accused Georgia on Friday of cutting gas deliveries to South Ossetia, deeming it "inhumane" to do so in winter.

Speaking to 50-odd foreign ministers gathered in Helsinki for a two-day meeting of the European security body OSCE, Lavrov urged the organisation "to prevent a humanitarian catastrophe."