Lee Jae-Joung told Yonhap news agency there were no signs that Pyongyang, which conducted its first underground nuclear test on October 9, would stage another.

"At present, no signs have been found yet," Lee said.

"Because it's well aware that a second nuclear test will turn the current situation from dialogue to tougher sanctions, I believe North Korea will not dare to conduct an additional nuclear test."

A South Korean foreign ministry official said Friday that activity had been detected at Punggye, near the site of the first test, but there were no signs yet of preparations for a second explosion.

The official was speaking after US television network ABC reported that North Korea appeared to have prepared for a repeat blast. The first sparked worldwide concern and United Nations sanctions.

On Sunday, Chung Hyung-Keun, a South Korean opposition lawmaker who was a deputy spy agency chief in the 1990s, said unusual personnel and construction activity had recently been detected at Punggye.

Chung said North Korea was fully prepared for a repeat test but was unlikely to go ahead pending the outcome of upcoming talks.

The latest round of six-nation talks on the North's nuclear programme ended in Beijing in December without a breakthrough. The US State Department said Friday the talks could resume as early as this month.

Financial officials from North Korea and the United States are scheduled to meet separately, possibly this month, to try to resolve a row over US financial sanctions imposed over the North's alleged counterfeiting and other illegal activities.