The United States on Thursday imposed sanctions on members and affiliates of Iran's Islamic Revolutionary Guard and its external operations arm, the Quds Force.

Washington accused those sanctioned of participating in terrorist plots targeting former US government officials, dual US and Iranian nationals and Iranian dissidents.

Former US Secretary of State Mike Pompeo and former national security adviser John Bolton have been targets of Iranian assassination plots.

The US Treasury Department said the move targeted three Iran- and Turkey-based individuals and a company affiliated with the IRGC-Quds Force and two senior officials of the IRGC's Intelligence Organization involved in plotting external lethal operations against civilians, including journalists.

The Treasury said the five included Mohammad Reza Ansari, a Quds Force member whom it said has supported its operations in Syria, and Iranian citizen Shahram Poursafi, whom it said had planned and attempted to assassinate two former US government officials.

It also put sanctions on Hossein Hafez Amini, a dual Iranian and Turkish national based in Turkey, whom it accused of using his Turkish-based airline, Rey Havacilik Ithalat Ihracat Sanayi Ve, to assist the Quds Force's covert operations, including kidnapping and assassination plots targeting Iranian dissidents.

The airline was also placed under sanctions.

The Treasury Department also said it had imposed penalties on two people linked to the IRGC's Intelligence Organization, which it described as a domestic and international unit focused on targeting journalists, activists, dual Iranian nationals, and others who oppose Iranian abuses and human rights violations.

It named these as Rouhallah Bazghandi, the former chief of the Intelligence Organization's counterespionage department, and the Intelligence Organization's chief, Reza Seraj.