WASHINGTON — The United States imposed sanctions on nine people with ties to Iran's Supreme Leader Ayatollah Ali Khamenei, including his chief of staff, one of his sons and the head of Iran's judiciary, the US Treasury Department said on Monday.

The United States also sanctioned Iran's Armed Forces General Staff, the department said in the statement, which came 40 years after Iran seized the US embassy in Tehran, taking more than 50 Americans hostage.

"Today the Treasury Department is targeting the unelected officials who surround Iran’s Supreme Leader, Ayatollah Khamenei, and implement his destabilizing policies," US Treasury Secretary Steven Mnuchin said in a statement.

"These individuals are linked to a wide range of malign behaviors by the regime, including bombings of the US Marine Barracks in Beirut in 1983 and the Argentine Israelite Mutual Association in 1994, as well as torture, extrajudicial killings, and repression of civilians," Mnuchin added.

Separately, the US State Department announced a new reward up to $20 million for information that leads to the location, recovery and return of Robert Levinson, a former FBI agent who was last seen in Iran.

"The Trump Administration has made clear that the regime in Iran must release all missing and wrongfully detained Americans, including Robert Levinson, Xiyue Wang, Siamak Namazi, and others. We will not rest until they are reunited with their families," Secretary of State Mike Pompeo said in a statement, referring to American citizens who have been imprisoned in Iran after being accused of espionage.

The sanctions are designed to impose more limits on Khamenei's inner circle, an administration official said.

"Our action is specifically focused on further targeting the financial assets of the supreme leader’s inner circle of both military and foreign affair advisors,” a senior administration official said in a call with reporters to discuss the sanctions.

Those targeted by the US sanctions include Khamenei's chief of staff Mohammad Mohammadi Golpayegani as well as Vahid Haghanian, who the department said "has been referred to as the Supreme Leader’s right hand."

Ebrahim Raisi, who Khamenei appointed in March 2019 to lead Iran’s judiciary, and Mojtaba Khamenei, Khamenei's second son, were also sanctioned, Treasury said.

US sanctions block any US-controlled property or interests held by those targeted, and prohibit anyone or any entities in the United States from dealing with those sanctioned.

The Iranian mission to the United Nations did not immediately respond to a request for comment. — Reuters