Iran’s semi-official Tasnim news agency claimed Wednesday that Israel was responsible for the death of UN nuclear watchdog chief Yukiya Amano several days ago at the age of 72.

The Tehran-based outlet, which defines its mission as “defending the Islamic Revolution against negative media propaganda campaign [sic],” cited unnamed “informed sources” who insisted that Amano, a Japanese diplomat who was extensively involved in negotiations over Iran’s controversial nuclear program, had been “eliminated” after refusing to buckle to “heavy pressure” from Jerusalem and Washington.

The International Atomic Energy Agency dismissed the Tasnin report. It told The Times of Israel: “[We] categorically deny these false reports. Director General Yukiya Amano passed away on 18 July as a result of his illness.”

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Amano’s death comes at a time of increasing concerns and escalating tensions over Iran’s nuclear program, after US President Donald Trump left a 2015 deal with world powers that restricted the country’s nuclear uranium enrichment.

Amano was heavily involved in the years-long negotiations that led to the landmark Iran nuclear deal.

“There is evidence that the Trump administration and the Israeli regime were constantly pressuring the Japanese diplomat to accuse Iran of violation of the 2015 nuclear deal,” the Tasnim report said. But Amano refused “to open a false case against Iran on the nuclear issue,” Tasnim quoted its sources as saying.

The Iranian mouthpiece offered no proof for its assertions.

The International Atomic Energy Agency announced Amano’s death on Monday. He had wide experience in disarmament, non-proliferation diplomacy and nuclear energy, and had been chief of the key UN agency that regulates nuclear issues worldwide since 2009. The IAEA Secretariat did not give a cause of death for Amano, or say where or when he died.

Two European diplomats, who spoke on condition of anonymity, said he had cancer.

A graduate of the Tokyo University Faculty of Law, Amano joined the Japanese Foreign Ministry in 1972 and was posted to jobs in Belgium, France, Laos, Switzerland, and the United States. At the Foreign Ministry, Amano was chief of the Disarmament, Non-Proliferation and Science Department from 2002 until 2005. He then served as Japan’s representative to the IAEA until his election as director general in July 2009, including a stint as chair of its board of governors in 2005-2006.

Agencies contributed to this report.