TEHRAN, Iran -- Iran hanged a man who was allegedly behind an attack that killed dozens of people at a military parade in the southern province of Khuzestan in 2018, state media reported on Saturday.

The execution was carried out in Tehran after a top court upheld a death sentence for Farajollah Cha’ab in March, Iran's state TV reported.

He was “the main person in the terrorist attack” at the parade in September 2018, authorities said, and was arrested by Iranian agents in 2020 after he left Sweden for Turkey. He is alleged to be the leader of a separatist group.

Cha’ab, who holds Iranian and Swedish citizenship, disappeared under mysterious circumstances in Turkey in November 2020.

In September 2018, militants disguised as soldiers opened fire on an annual military parade in Ahvaz, the capital of oil-rich Khuzestan. At least 25 people were killed and 70 wounded, including a 4-year-old boy.

Iran then claimed that Saudi Arabia and Israeli intelligence services supported what it says was an attack by the separatist group.