North Korea making nuclear progress, says South
South Korea's defence ministry has speculated that the North has made progress towards making deliverable nuclear weapons.
In a white paper, the ministry said enough time had passed since the North's first nuclear test for it to have acquired the technology.
A ministry official, however, told the Yonhap News agency that there was no intelligence to support the assessment.
Meanwhile North Korea's leader said he was open to talks with the South.
"North Korea's capabilities of miniaturising nuclear weapons appear to have reached a significant level," the paper said.
Miniaturising a nuclear device would allow it to be fitted on the tip of a long-range missile which could, in theory, reach South Korea or even the US.
An unnamed defence ministry official told Yonhap: "We don't have any intelligence that North Korea completed the miniaturisation."
But the official said acquiring such technology took between two and seven years, and it had been eight years since the North conducted its first nuclear test.
Pyongyang has conducted three nuclear tests with the most recent in February 2013.
Expert opinion is split on how much progress the North's ballistic missile development programme has made.
'Highest level' talks
The white paper also said that the North was "presumed to have (missiles) capabilities that could threaten the US mainland, having fired off long-range missiles five times."
However, the official said no signs had been seen yet that Pyongyang had put long range missiles into service.
North and South Korea are technically still at war since no peace treaty was signed after their 1950-53 conflict.
North Korean leader Kim Jong-un said in a New Year's Day address that he was open to the "highest level" talks with South Korea but only under certain conditions.
He said the South should end its joint military exercises with the US and stop "slandering" the North, which is facing criticism from the international community for its human rights record.
Recently, the US accused North Korea of hacking Sony over the release of a comedy film about journalists recruited to assassinate North Korean leader Kim Jong-un.