Military experts say new missiles that North Korea reportedly has developed are likely to be more accurate than its older weapons. The technology for the new missiles apparently went to North Korea from Russia via Japanese scrap dealers.
The respected military publication Jane's Defense Weekly says North Korea based the new missiles on the SSN6 system used in old Soviet submarines.
Futoshi Shibayama, a defense expert at Japan's Aichi Gakuin University, says missiles based on the SSN6 system would be an improvement over the Taepodong missile the communist state already has.
"In terms of the range it's hardly different. But in terms in reliability and in terms of how much [accuracy] you can get the target the latter missile is having more credibility," he said.
Jane's says the missiles have a range of at least 2500 kilometers, and the modified North Korean version possibly could be launched from land or from a ship at sea. That means it could reach both Japan and parts of the United States.
News of the new missile comes as the United States and four other countries are pushing North Korea to abandon efforts to build nuclear weapons.
Experts say North Korea's biggest challenge in its nuclear program has been to make bombs light enough to be carried on its missiles.
Professor Shibayama says that if Pyongyang does develop a small bomb, alarm bells would ring in Washington, Seoul and Tokyo.
"As long as North Korea can have a missile which can carry the nuclear warhead to the U.S. soil, even Hawaii, Guam [the U.S. territory], that is going to be a big deterrent power," Prof. Shibayama said.
U.S. officials last year said North Korea was working with the SSN6 technology.
The Jane's report says North Korea gained valuable data after it purchased 12 decommissioned Russian submarines from Japanese scrap dealers more than a decade ago. It says the submarines still had significant elements of missile system, including launch tubes and stabilization sub-systems.
There has been no comment from the Japanese government or law enforcement agencies about a possible Japan connection. But analysts say they expect the news will prompt an investigation.
Six years ago North Korea shocked Japanese when it launched a Taepodong missile over Japan. Since then, Japan's government has begun improving its ability to defend against missile attacks.