A leaked United Nations report suggests North Korea and Iran have been exchanging ballistic missile technology in violation of UN sanctions.
The report, obtained by Reuters and reported by the BBC, says regular transfers have been taking place through "a neighbouring third country", named by a diplomat as China.
The sanctions - imposed by the UN on North Korea after it conducted a series of nuclear tests in 2006 and 2009 - ban all trade in nuclear and missile technology with North Korea.
The UN also imposed an arms embargo and subjected some North Korean individuals to travel bans and froze their assets.
North Korea has twice tested nuclear devices and revealed last September that it had entered the final phase of uranium enrichment.