Seoul's Ministry of National Defense says it remains unconvinced of North Korea’s recent announcement that it miniaturized nuclear warheads for use on ballistic missiles.

Ministry Spokesman Moon Sang-gyun said in a news briefing on Monday that there is no change in the ministry’s stance that the North has not yet developed the capability. 

He said it is believed that Pyongyang has yet to possess nuclear warheads small enough to mount on missiles, although its miniaturization technology appears to have reached a significant level.
 
Recently, some experts have raised the possibility that the North may have a means to the technology to make small nuclear warheads. Jeffrey Lewis, a director at the James Martin Center for Nonproliferation Studies, said in a contribution to the North Korea-focused U.S. Web site 38 North that Pyongyang may have nuclear warheads that are 60 centimeters in diameter and weigh between 200 to 300 kilograms.
 
The ministry spokesman, meanwhile, declined to comment on international media reports over the weekend regarding a North Korean submarine that allegedly went missing. Moon quoted South Korean and U.S. intelligence authorities as saying that they cannot confirm the report.