Iran said Saturday it executed eight people convicted in the 2017 Daesh terror group attack on parliament and the shrine of Ayatollah Ruhollah Khomeini in Tehran.

The June 7, 2017 attack has so far been the only assault by the terror group inside of Iran, which has been deeply involved in the wars in Iraq and Syria where the terrorists once held vast territory.

The judiciary's official Mizan news agency and semi-official news agencies in Iran acknowledged the executions Saturday, but did not say when they took place. Executions in Iran are carried out by hangings.

While Iran is one of the world's top enforcers of the death penalty, such mass executions are rare. In August 2016, human rights activists criticized Iran for carrying out the mass execution of 20 members of a terror group identified as Jihad and Tawhid after a six-year trial. In August 2007, Iran hanged seven men convicted of rape in Mashhad at the same time.

Mizan noted in its report that the executions came after the eight men had been tried and convicted in a trial that included both eyewitness testimony and video footage showing their involvement.

"These eight worked directly ... in killing and wounding a number of innocent compatriots," Mizan said.

The news agencies on Saturday named those executed as Soleiman Mozafari, Esmail Sufi, Rahman Behrouz, Majed Mortezai, Sirous Azizi, Ayoub Esmaili, Khosro Ramezani and Osman Behrouz.

Daesh attack killed at least 18 people and wounded more than 50. It saw gunmen carrying Kalashnikov assault rifles and explosives storm the parliament complex where a legislative session had been in progress, starting an hourslong siege.

Meanwhile, gunmen and suicide bombers also struck outside Khomeini's mausoleum on Tehran's southern outskirts. Khomeini led the 1979 revolution that toppled the Western-backed shah to become Iran's first supreme leader until his death in 1989.

The assault shocked Tehran, which largely has avoided militant attacks in the decades after the tumult surrounding the revolution.

Over a dozen others remain on trial over the attack. Iran's paramilitary Revolutionary Guard responded to the attack by launching six missiles into eastern Syria targeting Daesh terrorists.

Iran was second only to China in 2017 in the number of known executions carried out, according to Amnesty International. Iran executed over 500 people last year, according to the group.

The Daesh executions come as controversy still swirls in Iran surrounding the country's mass executions of 1988 near the end of the Iran-Iraq War. Activists at the time said Iran executed as many as 5,000 people after sham trials of Communists, Kurdish separatists, political prisoners and members of an Iranian exile group known as the Mujahedeen-e-Khalq.

The executions represent one of the darkest moments of Iran's post-revolution history and are still not recognized by its government.