On January 3, a US drone strike in Iraq killed Soleimani, leader of the Revolutionary Guards' Quds Force. Washington blamed Soleimani for masterminding attacks by Iran-aligned militias on US forces in the region.

"Mahmoud Mousavi-Majd, one of the spies for the CIA and the Mossad, has been sentenced to death ... He had shared information about the whereabouts of martyr Soleimani with our enemies," judiciary spokesman Gholamhossein Esmaili said in a televised news conference.

"He passed on security information to the Israeli and American intelligence agencies about Iran's armed forces, particularly the Guards," Esmaili said.

Esmaili said Mousavi-Majd's death sentence had been upheld by a supreme court and "he will be executed soon".

Later, the judiciary said in a statement that Mousavi-Majd's conviction was not linked to "the terrorist act of the US government" in Soleimani's killing in Iraq.

"All the legal proceedings in the case of this spy ... had been carried out long before the martyrdom of Soleimani," the statement said, adding Mousavi-Majd had been arrested in October 2018.

Officials have not said whether Mousavi-Majd's case is linked to Iran's announcement in the summer of 2019 that it had captured 17 spies working for the CIA, some of whom it said were sentenced to death.

Nor have they said whether Mousavi-Majd's case is linked to Iran's announcement in February of this year that Iran had sentence to death a man for spying for the CIA and attempting to pass on information about Tehran's nuclear program.

Soleimani's killing led to a peak in confrontation between Iran and the United States. Iran retaliated with a rocket attack on an Iraqi air base where US forces were stationed. Hours later, Iranian forces on high alert mistakenly shot down a Ukrainian passenger airliner taking off from Tehran.

Australian Associated Press