VIENNA — The U.N. atomic agency expressed alarm Monday about Iran’s decision to bar some of its inspectors, suggesting that its efforts to monitor the country’s nuclear program were suffering as a result.

The unusually blunt International Atomic Energy Agency warning was voiced in a restricted report on Iran that otherwise contained few surprises. It followed Iran’s recent decision to strip two experienced inspectors of the right to monitor its nuclear activities after the two reported what they said were undeclared nuclear experiments.

The Islamic Republic says the reporting by the two was inaccurate, but the IAEA stands by the findings. And the 11-page IAEA document issued Monday devoted a special section to the complaint, reflecting the importance attached to it by IAEA chief Yukiya Amano.

Such a section was included in only one previous report, after Iran stripped the right of dozens of inspectors in 2006 and 2007 – most of them in order to show displeasure over recently passed U.N. Security Council sanctions on the Islamic Republic.

Monday’s report said that objections by Iran to some experienced inspectors “hampers the inspection process and thereby detracts from the Agency’s capability to implement effective and efficient safeguards in Iran.”

Diplomats from three countries accredited to the agency echoed the IAEA’s concerns, saying Iran appeared keen to ban seasoned inspectors — particularly those from nuclear weapons countries with special skills that could help detect attempts to make nuclear arms.

And a U.N. official who was a former IAEA inspector in Iran spoke of intense scrutiny while on such missions and the fear among inspectors that they would be banned from returning if they reported something the Iranians did not like.

“If you opened your eyes too much you ran the risk of being de-designated” by the Iranians said the official, who asked for anonymity because his information was confidential.

He said he agreed with the concerns that Iran was weeding out experts most likely to discover secret programs designed to make weapons.

“The IAEA doesn’t teach you about weaponization,” he said. “Only experts from weapons countries are good at that kind of thing.”

Iran rejected allegations of selective bans and intimidation of IAEA inspectors, with Ali Asghar Soltanieh, Tehran’s chief delegate to the agency calling them “absolutely unjustified.”