REUTERS - Russian Prime Minister Vladimir Putin made a surprise visit to the breakaway region of Abkhazia on Wednesday, pledging half a billion dollars to strengthen the defences of the Moscow-backed rebel enclave.

Russia recognised Abkhazia and another breakaway region, South Ossetia, as independent states last year after Russian troops repelled a Georgian attempt to retake South Ossetia in a five day war which ended on Aug. 12, 2008.

Tensions have been rising along the de facto borders between the regions and Georgia proper, raising concerns that another conflict could be easily sparked.

"With today's Georgian leadership, you cannot rule anything out," Putin said in an interview with Abkhaz reporters when asked if there would be a repeat of last year's war.

Putin, who arrived by helicopter in the local capital Sukhumi, said Russia would spend 15-16 billion roubles ($500 million) in 2010 on strengthening Abkhazia's defences, including shoring up its borders and equipping Russian military bases.

"We will make the necessary efforts together with the corresponding Abkhaz structures to build a modern border defence," Putin said in the interview, a copy of which was supplied by his press service to reporters.

"This is an additional and serious guarantee of the security of Abkhazia and South Ossetia," he said, adding that Russia would provide an additional 2.5 billion roubles in aid next year to support the Abkhaz budget.

The rest of the world -- apart from Nicaragua -- still views Abkhazia and South Ossetia as part of Georgia, though Russia has deployed several thousand troops to the regions and has military bases in both enclaves.

Russia-backed region

Putin's visit, during a break from his vacation in the Black Sea resort of Sochi, underscores Russia's strengthening foothold in the rebel regions, whose populations are ethnically distinct from Georgians and look to Moscow for support.

The European Union last month criticised a visit by Russian President Dmitry Medvedev to South Ossetia and said it supported Georgia's territorial integrity. The United States has called for Georgia's sovereignty to be respected.

Both regions broke away from Georgia's rule after wars in the early 1990s and have run their own affairs ever since. They are heavily dependent on Russia.

Pro-Russian billboards -- "Russia and Abkhazia: together for prosperity" -- dotted the streets of Sukhumi, which is nestled among vineyards and orchards on the Black Sea coast.

Putin planned to lay a wreath at a cenotaph in honour of those who fell in a 1992-1993 war. He was also due to visit a maternity hospital.

Putin said he had last visited Abkhazia in Soviet times, when the coast was a popular holiday destination, to work as part of a student labour brigade.

"I earned what was in those times an enormous sum -- 800 roubles. With the money, I bought an overcoat which I wore for 15 years," Putin said.