Iran said it had foiled a sabotage attack on an atomic energy agency building on Wednesday, shortly after slamming Washington's blockage of dozens of Iranian media sites as unhelpful for ongoing nuclear talks.

State television said the thwarted "sabotage operation" targeted a building belonging to the Atomic Energy Organization of Iran, without identifying the operation's nature or the culprits.

"The saboteurs failed to carry out their plan," and there were no casualties or damage, state TV reported.

A file photo taken on October 26, 2010 shows the reactor building at the Russian-built Bushehr nuclear power plant in southern Iran A file photo taken on October 26, 2010 shows the reactor building at the Russian-built Bushehr nuclear power plant in southern Iran Photo: MEHR NEWS / MAJID ASGARIPOUR

Tasnim news agency said the target building was near the city of Karaj, some 50 kilometres (30 miles) west of the capital Tehran.

The reports came as talks continue in Vienna between Tehran and world powers aimed at reviving their hobbled 2015 nuclear deal, staunchly opposed by Israel, Iran's arch-nemesis and a key ally of the US.

The reported sabotage also comes a day after the US Justice Department said it had seized 33 Iranian government-controlled media websites, alleging they were hosted on US-owned domains in violation of sanctions.

This image taken from presstv.com announces that the Iranian website was seized by US authorities on June 22, 2021 This image taken from presstv.com announces that the Iranian website was seized by US authorities on June 22, 2021 Photo: presstv.com / -

The office of Iran's outgoing president Hassan Rouhani warned on Wednesday that Washington's move was "not constructive" for the nuclear talks, even as Germany's top diplomat Heiko Maas said there was a "good chance" of reviving the deal soon.

An Iranian youth shows on his mobile phone a statement declaring the website of Iran's Arabic-language channel Al-Alam has been seized by the US government An Iranian youth shows on his mobile phone a statement declaring the website of Iran's Arabic-language channel Al-Alam has been seized by the US government Photo: AFP / -

The developments come days after ultraconservative cleric Ebrahim Raisi was elected Iran's next president, in an election the US deplored as neither free nor fair.

The 2015 nuclear deal promised Iran sanctions relief in return for limits on its nuclear programme, but was torpedoed three years later when then US-president Donald Trump unilaterally withdrew from it and reimposed punishing sanctions.

In response, Iran later progressively stepped back from its own commitments under the deal.

Iran, which is engaged in talks with world powers on rescuing the landmark 2015 nuclear deal, alleged it foiled another nuclear related sabotage attempt on Wednesday Iran, which is engaged in talks with world powers on rescuing the landmark 2015 nuclear deal, alleged it foiled another nuclear related sabotage attempt on Wednesday Photo: AFP / ATTA KENARE

Israel has always vigourously opposed the deal, and its new coalition government has pledged to "do whatever it takes to prevent Iran obtaining a nuclear bomb".

Iran has always denied seeking nuclear weapons.

Tehran accuses the Jewish state of being behind a sabotage attack on its Natanz uranium enrichment plant in April and the assassination of its top nuclear scientist Mohsen Fakhrizadeh last November.

Israel has never commented on that killing, and neither confirmed nor denied involvement in the "small explosion" at Natanz. But Israeli public radio said the latter was a sabotage operation by the Mossad spy agency, citing unnamed intelligence sources.

IMAGES US Secretary of State Antony Blinken arrives for a press conference in Berlin with German Foreign Minister Heiko Maas ahead of peace talks on Libya. World powers are gathering in the German capital to ensure that the conflict-wracked North African IMAGES US Secretary of State Antony Blinken arrives for a press conference in Berlin with German Foreign Minister Heiko Maas ahead of peace talks on Libya. World powers are gathering in the German capital to ensure that the conflict-wracked North African country stays firmly on the path towards general elections on December 24. Photo: GERMAN POOL

The New York Times also quoted intelligence sources pointing to a "an Israeli role".

Iran's foreign ministry accused Israel of an act of "nuclear terrorism" over Natanz, aimed at scuttling the Vienna talks.

The Vienna dialogue has been spurred by Trump's successor Joe Biden favouring rejoining the accord, even if Tehran and Washington have officially yet to negotiate directly to that end.

President-elect Raisi, seen as close to supreme leader Ayatollah Ali Khamenei who holds ultimate political power in Iran, said on Monday he would not allow the nuclear negotiations to drag out forver.

He is set to replace Rouhani, a moderate who has served the maximum of two consecutive four-year terms, in August.

Germany, which remains a party to the Iran nuclear agreement alongside China, the UK, France and Russia, struck an upbeat note on Wednesday, while acknowledging challenges remained.

"Regarding the negotiations in Vienna, they aren't easy -- that's been clear in recent weeks," Foreign Minister Heiko Maas told journalists in Berlin during a visit by US Secretary of State Antony Blinken.

"Nevertheless we are moving forward step by step in every round of negotiations and we assume that in the context of the (Iranian) presidential election, there's a good chance to conclude them in the foreseeable future."

But Iran warned that the US decision on Tuesday to block dozens of Iran-linked websites was unhelpful for the talks and accused Washington of repressing freedom of expression.

Iranian media sites Press TV and Al-Alam, the country's main English- and Arabic-language broadcasters, were among those affected.

"We are using all international and legal means to... condemn... this mistaken policy of the United States," the director of Rouhani's office, Mahmoud Vaezi, told reporters.

"It appears not constructive when talks for a deal on the nuclear issue are under way."

Wednesday's alleged sabotage attack comes two days after Iran said it had temporarily shut down its only nuclear power plant at Bushehr on the country's Gulf coast, for maintenance work.