N Korea vows to boost nuclear deterrent

North Korea on Sunday denounced US-South Korean military drills near the tense border as a \"provocation\" and vowed to \"further bolster up its nuclear deterrent\", state media reported. Some 2,000 South Korean and US troops along with jet fighters, tanks and attack helicopters took part in the live-fire exercise Friday to test responses to any North Korean attack, amid high tensions on the peninsula. The allies on Saturday also launched a massive naval exercise in the Yellow Sea, ahead of the 62nd anniversary Monday of the outbreak of the Korean War. North Korea\'s foreign ministry accused the allies of firing at the North Korean flag. \"It is an extremely grave military action and politically-motivated provocation to fire live bullets and shells at the flag of a sovereign state without a declaration of war,\" the ministry said in a statement carried by the official Korean Central News Agency. \"The DPRK (North Korea) will further bolster up its nuclear deterrent for self-defence as long as the US, the world\'s biggest nuclear weapons state, persists in its hostile policy towards the DPRK,\" it said. Tensions are high after the North\'s failed rocket launch in April, seen by the United States and its allies as an attempted ballistic missile test. Pyongyang has also threatened attacks on the South\'s government and conservative media for perceived insults to its regime. The North has been developing nuclear weapons for decades. Its official position has been that it needs them for self-defence against a US nuclear threat, but that it is willing in principle to scrap the atomic weaponry. Under a September 2005 deal reached during six-nation negotiations, Pyongyang agreed to dismantle its nuclear programmes in return for economic and diplomatic benefits and security guarantees. But six-party talks on implementing the deal have been stalled since December 2008. The North has staged two nuclear tests, in 2006 and 2009. The three-day annual US-South Korean naval drill will involve 10 South Korean warships plus the USS George Washington aircraft carrier, 8,000 personnel and hundreds of combat aircraft, the defence ministry in Seoul said.