North Korea says forced to build nuclear might: Ifax

North Korea's foreign minister said that US and South Korean hostility was forcing Pyongyang to strengthen its nuclear deterrent, the Interfax news agency reported on Friday.

"We believe that until the United States and South Korea stop their hostile and confrontational policy toward the DPRK, it will be absolutely impossible to lift the tension from the Korean Peninsula," Interfax quoted foreign minister Pak Ui-chun as saying in an interview.

"And we are again convinced of the rectitude of our choice in favour of a policy of ... universal strengthening of our defence potential with a focus on nuclear deterrent forces," Pak, due to visit Russia next week for talks, was quoted as saying.

Tension increased after the North bombarded a South Korean island last month, killing four people, and revealed advances in its nuclear programme opening another route to making an atomic bomb.

The bombardment was the first time the North hit a civilian area on South Korean soil since the Korean war.

The US and South Korean militaries held large-scale joint exercises days later in a show of force they said was meant to deter Pyongyang from further military actions.

South Korea has vowed to hit back hard if Pyongyang orders a new attack, bolstering defences in a disputed area and amending rules of engagement to permit the use of fighter jets and bombs.

Reclusive North Korea has conducted two nuclear tests -- in 2006 and 2009 -- and is believed to have enough fissile material to make between six and 12 bombs.

Russia shares a short border with North Korea, which was a beneficiary of Soviet largesse during the Cold War, but has less influence on Pyongyang than China.

As one of the participants in long-stalled six-nation talks aimed at ending the confrontation over North Korea's nuclear programme, Russia repeatedly emphasises that it is crucial for all sides to refrain from military action.