Iran's foreign ministry on Tuesday rejected a UN panel report alleging that it has been exchanging ballistic missile expertise and components with North Korea in violation of UN sanctions.

"We have always rejected as propaganda and fabrications (reports) of cooperation between us and North Korea on the transfer of technology or transfer of ballistic missile components," ministry spokesman Ramin Mehmanparast told a weekly briefing.

He said that Iran's missile capabilities had reached "such a level that we do not need the technology and spare parts from other countries."

Mehmanparast was speaking in response to a UN sanctions report, which Beijing is seeking to block, that says Tehran and Pyongyang are suspected of sharing ballistic missile technology.

Diplomats said a Chinese representative on a UN panel of seven experts on North Korea nuclear sanctions refused to sign on to the report, which said prohibited material was moved through a "neighbouring third country."

The country is not named in the report, excerpts of which were passed to AFP, but diplomats said it was China, North Korea's closest ally and Iran's main trade partner.

China had blocked an earlier report in February which called for additional sanctions against Pyongyang, already under two sets of sanctions for conducting two atomic tests in 2006 and 2009.

Iran says its missile programme is home-grown but Western analysts say some of its weapons are derivatives of North Korean models.

Combined with its controversial nuclear programme, Iran's ballistic programme has raised concerns that it might acquire the know-how for a delivery system for a nuclear warhead, an ambition Tehran strongly denies.