The International Atomic Energy Agency (IAEA) froze 22 out of 55 technical cooperation projects with Iran, the UN nuclear watchdog said in a report to its 35-nation board in Vienna.
The IAEA followed the line laid out in UN Security Council resolution 1737 from December 23, 2006, which asks to suspend all cooperation that could potentially enable Iran to acquire a nuclear weapons capability.
The release of the report on Friday comes at the same time as Iranian chief nuclear negotiator Ali Larijani cancelled meetings both with IAEA Director General Mohamed ElBaradei in Vienna and his participation in a security conference in Munich, where he was expected to meet with senior European leaders.
According to conference organisers, Larijani cancelled his trip due to "health reasons".
The Security Council resolution prohibits all UN member states as well as the IAEA from giving Iran technical assistance on proliferation-sensitive activities such as uranium enrichment or fuel reprocessing.
Iran's IAEA envoy Ali-Asqar Soltanieh called the freeze a follow-on to the "legally unjustifiable" UN resolution and therefore technically not relevant.
"The UN resolution has caused the IAEA limitations and eventually led to the freezing of projects with Iran," Soltanieh said.
The report stressed that "the secretariat will continue to keep all its technical assistance activities under review to ensure that none contribute to Iran's proliferation-sensitive nuclear activities as specified in the resolution."
"Technical cooperation to Iran may proceed through 11 national projects and 20 regional and two inter-regional projects," the report said.
Of the 22 halted projects, 10 were suspended completely.
For the remaining 12, cooperation was suspended for disparate activities "except for those specific activities that, after a case-by-case screening by the secretariat upon receipt of a request for specific assistance, are found to be in conformity" with the UN resolution.
Among the projects Iran requested were technical assistance for developing a waste disposal facility and aid for the production of radiopharmaceuticals for cancer therapy.
Technical cooperation would continue only "if it is for food, agricultural, medical, safety or other humanitarian purposes" or where it related to light water reactors, as specified by the Security Council, the report said.