Iran was under fresh scrutiny Wednesday, November 9, after the UN atomic watchdog released reams of what it called "credible" intelligence suggesting Tehran had worked on developing nuclear weapons, AFP reported.

With Washington threatening to increase international pressure on Iran and Israel's president stoking speculation of a pre-emptive strike, the International Atomic Energy Agency report was set to stoke Middle East tensions.

The Vienna-based watchdog said it had "serious concerns" based on "credible" information indicating that the Islamic republic "has carried out activities relevant to the development of a nuclear explosive device."

Although some of the areas listed in 12 dense pages of intelligence "have civilian as well as military applications," the keenly-awaited report said that "others are specific to nuclear weapons."

Activities included computer modeling of a nuclear warhead, testing explosives in a large chamber at the Parchin military base near Tehran and studying how to arm a Shahab 3 medium-range missile with an atomic warhead.

"The report details Iranian activities that can only be explained if the purpose was to develop a nuclear bomb," one Western diplomat in Vienna said.

Tehran's envoy to the Vienna-based agency, Ali Asghar Soltanieh, told the Iranian news agency Fars it was "a repetition of old claims which were proven baseless by Iran in a precise 117-page response."