Vietnam will have a submarine fleet within six years, the defence minister confirmed in reports on Thursday, as China's increasing maritime assertiveness causes regional concern. Russian media reported in December 2009 that Vietnam had agreed to buy half a dozen diesel-electric submarines for about two billion dollars, but Hanoi had not previously commented on the deal. "In the coming five to six years, we will have a submarine brigade with six Kilo 636-Class subs," Defence Minister Phung Quang Thanh was quoted as saying by the state-controlled Tuoi Tre newspaper. Thanh said the fleet was "definitely not meant as a menace to regional nations," according to Thursday's report. "Buying submarines, missiles, fighter jets and other equipment is for self-defence," he was quoted as saying, without specifying how Vietnam was paying for the naval investment. "It depends on our economic ability. Vietnam has yet to produce modern weapons and military equipment, which are costly to import," he said. Economists say the country's economy is in turmoil with galloping inflation, large trade and budget deficits, inefficient state spending, and other woes. Much of Vietnam's military hardware is antiquated but this week it received the first of three new coastal patrol planes for the marine police, announced the manufacturer, Madrid-based Airbus Military. When news of the Russian deal first emerged, analysts said the acquisition aimed to bolster Hanoi's claims against Beijing in the South China Sea, where the two sides have a longstanding territorial spat that has recently flared. Tensions were heightened in May when Vietnam accused Chinese marine surveillance vessels of cutting the exploration cables of an oil survey ship inside the country's exclusive economic zone. Other nations in the region have accused China in recent months of becoming more aggressive in enforcing its claims to parts of the South China Sea. The Philippines, Malaysia, Brunei and Taiwan also have overlapping claims to all or parts of the waters, believed to be rich in oil and gas deposits.