The United States believes Iran's Ministry of Intelligence and Security was directly involved in the killing of an Iranian dissident last November in Turkey, a senior administration official told Reuters news agency on Wednesday.

Masoud Molavi Vardanjani was shot dead on an Istanbul street on November 14, 2019. Citing Turkish officials, Reuters last week reported that two intelligence officers in Iran's consulate in Istanbul had instigated his killing.

"Given Iran's history of targeted assassinations of Iranian dissidents and the methods used in Turkey, the United States government believes that Irana's Ministry of Intelligence and Security (MOIS) was directly involved in Vardanjani's killing," a senior administration official told Reuters.

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The US had not previously disclosed its assessment on who might have been behind the incident.

A week after Vardanjani was killed, US Secretary of State Mike Pompeo described it as “another tragic example in a long string of suspected Iran-backed assassination attempts” of Iranian dissidents.

Late on Wednesday, Pompeo in a tweet said he found disturbing the reports that Iranian diplomats were involved in the killing of the dissident, but that they were "fully consistent" with their assignments.

"Iran's 'diplomats' are agents of terror and have conducted multiple assassinations and bomb plots in Europe over the past decade," Pompeo said.

A police report by the Turkish authorities into the killing, published two weeks ago, said Vardanjani had an “unusual profile.” It said he had worked in cybersecurity at Iran’s Defence Ministry and had become a vocal critic of the Iranian authorities.

Turkish authorities did not publicly accuse the Iranian government of involvement at the time, but the Turkish officials last week told Reuters that Ankara would now raise Vardanjani’s killing with Iran.

The US assessment comes amid its "maximum pressure" campaign against Tehran, through which President Donald Trump aims to force Iran to limit its missile programme and curb its use of proxy forces in Iraq, Yemen and Lebanon.

Tensions between the US and Iran have remained high since Trump in 2018 unilaterally pulled out of a 2015 nuclear deal to control Iran's nuclear programme.

In recent weeks, the US has repeatedly tightened sanctions on Iran, despite calls from Iranian authorities, the United Nations and China asking it to ease restrictions as the country battles the coronavirus pandemic.