|North Korea's shelling of Yeonpyeong island set off a regional crisis which diplomats are trying to resolve [EPA]
North Korea's foreign minister has travelled to Russia amid a flurry of diplomatic attempts to ease tensions following the North's deadly attack on a South Korean island last month.
Pak Ui-chun departed for Moscow on Saturday, the North's official news agency said, a day after defending his country's move to strengthen its nuclear weapons.
Pak accused South Korea and the US of pursuing a policy of hostility and confrontation and reiterated that North Korea needs its nuclear programme to fend them off.
"We once again feel convinced that we have made the right choice in strengthening our defences with the nuclear deterrent,'' he was quoted as saying by the Russian news agency Interfax.
The North's November 23 bombardment of the border island Yeonpyeong killed four people including two civilians.
Pyongyang said it fired in response to a South Korean artillery drill that dropped shells into its waters near the contested border. The South says the North's attack was pre-planned.
The shelling set off a regional crisis. China, the North's sole major ally, has come under intense international pressure to use its diplomatic clout to rein in North Korea.
James Steinberg, the US deputy secretary of state is scheduled to visit Beijing in the coming week to press the Chinese for stronger action.
The diplomatic activity comes as Lee Myung-bak, the South Korean president, expressed optimism during a trip to Malaysia that the reunification of Korea is drawing near.
"North Korea now remains one of the most belligerent nations in the world," Lee said in an interview published on Friday in the Malaysian newspaper The Star.
But he also said it is a "fact that the two Koreas will have to coexist peacefully and, in the end, realise reunification."
In a speech on Thursday night, Lee made similar remarks, saying North Koreans have become increasingly aware that the South is better off.
"Reunification is drawing near," Lee said, according to the presidential website.
He also called on China to urge North Korea to embrace the same economic openness that has led millions of Chinese out of poverty, and said that North Korean economic independence was the key to reunification.
The Korean peninsula was divided after the end of Japanese rule in 1945 and officially remains in a state of war because the Koreas' 1950-53 conflict ended with an armistice, not a peace treaty.
South Korean leaders often call for a peaceful reunification with the North. There is in Seoul, however, a wariness of the huge social and economic costs associated with absorbing the impoverished North.
North Korea also has called repeatedly for reunification, but it imagines integration under its authoritarian political system. It has shown no sign that it would allow any reunification that results in its absorption by the richer South.