The Telegraph quoted Iranian officials as saying that their country is particularly dependent on North Korean scientists, but people with expertise from African countries are also being recruited to work on developing missiles and nuclear production activities.
Mohamed Reza Heydari, a former Iranian consul in Oslo, said that he had personally helped a number of North Koreans enter the country while working for the foreign ministry's office in Tehran's Imam Khomenei airport.
"Our mission was to coordinate with a team from the Ministry of Intelligence in checking the visas of the foreign diplomatic and trade delegates who visited Iran, with special attention to VIPs," the paper quoted him, as saying.
"We had the instructions to forgo any visa and passport inspections for Palestinians belonging to Hamas and North Korean military and engineering staff who visit Iran on regular basis," Heydari added.
He further revealed that the North Koreans were all technicians and military experts involved in two aspects of Iran's nuclear programme. One to enable Iran to "achieve nuclear bomb capability", while the other is to "help increase the range of Iran's ballistic missiles."
Earlier, western officials had expressed alarm at the sophistication of a recently unveiled North Korean uranium enrichment facility near Yongbyon. North Korea built the new plant at Yongbyon without any prior warning, the paper said.
The plant's similarity to Iran's programme has raised alarm over the extensive co-operation between two countries that are subject to UN sanctions for violating nuclear proliferation rules, it added.