Tehran has no obligation to grant the UN's nuclear watchdog access to sites in Iran when it deems the requests are based on "fabricated information", Iran's UN ambassador in Vienna said on Wednesday.

Kazem Gharib Abadi also accused the United States and Israel of trying to "exert pressure on the agency ... in order to distort the proactive and constructive cooperation" between the IAEA and Iran.

"Intelligence services' fabricated information ... creates no obligation for Iran to consider such requests," said a statement from Iran's ambassador.

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It comments come a day after a report from the International Atomic Energy Agency (IAEA) reprimanded Iran for refusing access to two sites, which diplomats say could be connected to the country's historic nuclear activity.

Israel has claimed a trove of information obtained by its intelligence services contains new information on a previous nuclear weapons programme in Iran.

The two sites the IAEA was denied access to were among three locations that the agency had been raising questions over since the middle of last year.

The IAEA said in Tuesday's report that it had been sent a letter by Iran saying Tehran did "not recognize any allegation on past activities and does not consider itself obliged to respond to such allegations".

The three sites the IAEA reported on are in addition to another location in Tehran where the agency found uranium particles late last year.

IAEA Director General Rafael Grossi told AFP on Tuesday during a visit to Paris that he was "worried" by the possibility that there had been undeclared nuclear activity at that site and called on Iran to provide answers.

While the IAEA has not identified the site in question, diplomatic sources told AFP that the agency asked Iran about a site in the Turquzabad district of Tehran, where Israel has alleged secret atomic activity in the past.

The renewed focus on Iran's historic programme could add to the tension over its current nuclear activities.

A second IAEA report on Tuesday outlined Iran's continued breaches of the terms of the 2015 nuclear accord with world powers but did not report any restrictions in access to nuclear facilities.

The 2015 deal has been hanging by a thread since the US withdrew from it and re-imposed swingeing sanctions on Iran, prompting Tehran to progressively abandon the accord's restrictions on its nuclear activities.