Two judges were killed in a shooting attack on Saturday at the Supreme Court building in Tehran, state media reported.

"Three judges of the Supreme Court were targeted. Two of them were martyred," the Judiciary's Mizan Online website reported, adding that the "assailant killed himself."

State news agency IRNA also reported that one other person was injured in the attack.

Mizan identified the two slain judges as Ali Razini and Mohammad Moghisseh, adding that they worked on cases "fighting crimes against national security, espionage and terrorism."

The motive behind their killing was not immediately clear, but Mizan said the assailant was not involved in any cases before the Supreme Court, without providing further details on the attacker's identity.

Authorities said an investigation into the incident was launched, Mizan added.

Veteran judge Moghisseh, 68, was sanctioned in 2019 by the United States for having "overseen countless unfair trails, during which charges went unsubstantiated and evidence was disregarded," according to the US Department of the Treasury.

Razini, 71, held several important positions in Iran's judiciary and was previously targeted in a 1998 assassination attempt by assailants "who planted a magnetic bomb on his vehicle," according to Mizan.

In August 2005, renowned Iranian judge Hassan Moghaddas was murdered by two gunmen who climbed into his car in the middle of a busy business district in Tehran.

Two men convicted over his killing were publicly executed by hanging two years later. (AFP)