A leading Japanese daily says Iran received help from North Korean technicians when it built a nuclear reprocessing facility capable of extracting plutonium.

The Sankei Shimbun said Thursday that the during the past two years, North Korean nuclear technicians and experts have visited Iran to impart knowledge on the reprocessing technologies required to extract plutonium.

The paper added that Iran purchased machinery and parts needed for nuclear reprocessing through a business front, as Iran is prohibited from buying such weapons under U.N. Security Council sanctions.

In response to the daily’s report, the Iranian Embassy in Tokyo said Iran’s nuclear activities are being carried out peacefully in line with the Nuclear Nonproliferation Treaty, denying any collaboration with North Korea on nuclear technology.