SEOUL: North Korea has warned of nuclear retaliation against any US and South Korean nuclear threats, in fresh criticism of an upcoming military drill between the allies, state media said Sunday.

A spokesman for Pyongyang's military denounced the exercises starting Monday as "manoeuvres for a nuclear war" against North Korea.

"Should the US imperialists and the Lee Myung-Bak group threaten the DPRK (North Korea) with nukes, it will retaliate against them with nukes," said the spokesman, referring to South Korea's president.

"If they threaten the DPRK with missiles, it will react to them with missiles," he said.

The spokesman added: "If they tighten 'sanctions' and push 'confrontation' to an extreme phase, the DPRK will react to them with merciless retaliation of its own style and an all-out war of justice." Toughened international sanctions were imposed on North Korea following its long-range rocket launch in April and its second nuclear test in May.

The warning from Pyongyang came in a statement issued on Saturday by the spokesman at the inter-Korean border village of Panmunjom. It was published on Sunday by the official Korean Central News Agency.

Seoul and Washington have denied having any plans to invade North Korea, saying the drill, from August 17-27, is defensive in nature.

US and South Korean military authorities last month informed North Korea of their plan to hold the joint military drill, which will involve 10,000 US soldiers and an unspecified number of South Korean troops.

They said the Ulchi Freedom Guardian (UFG) annual military drill involves computer-simulated war games designed to improve the allies' ability to defend South Korea from attack.

The two Koreas remain technically at war after their 1950-1953 conflict ended in an armistice, not a peace treaty.

More than 600,000 South Korean soldiers, backed by 28,500 US troops, are deployed in the southern part of the peninsula, confronting a potential threat from the North's 1.1 million-strong military.

South Korean President Lee on Saturday called for talks with North Korea aimed at ridding the Korean peninsula of nuclear weapons as well as making cuts in conventional weapons.

After the UN Security Council censured its April 5 long-range rocket launch, the North announced it was quitting the six-party nuclear disarmament talks and restarting its plutonium-producing programme.

It staged its second nuclear test on May 25.

A North Korean envoy to the United Nations said last month Pyongyang was, however, open to direct talks with Washington. The US has said this is possible within the context of the six-party forum.

The talks grouping the two Koreas, China, Russia, the United States and Japan became deadlocked last December.

Philip Goldberg, a US special envoy responsible for implementing sanctions, will Thursday begin his tour which will bring him to Singapore, Thailand, South Korea and Japan to put pressure on North Korea, Yonhap news agency said.

State Department spokesman Philip Crowley said Friday that to bring North Korea back to negotiations on halting its nuclear programme would be complex but is still possible.