North Korean state media on Friday said leader Kim Jong Un had overseen the testing of a "newly-developed high-tech weapon," according to South Korean Yonhap news agency.

"Kim Jong Un inspected the testing of a newly-developed high-tech tactical weapon at the Academy of National Defence Science," Yonhap cited the North's state broadcaster as saying.

Yonhap said Korean Central Television (KCTV) had reported that the test was successful and the new weapon had been "researched and developed for a long time," without elaborating.

Pyongyang's suspension of nuclear weapon and ballistic missile tests has been key to this year's rapid diplomatic developments and North Korean-U.S. negotiations, and a return to testing would cast doubts over the future of the process.