Farajollah Cha’ab, an Iranian-Swedish dual national accused of masterminding a 2018 attack on a military parade in Iran that killed at least 25 people, has been executed by Iran.

Cha’ab was identified as the leader of the Arab Struggle Movement for the Liberation of Ahwaz, an Arab separatist group that has conducted several attacks in Iran’s oil-rich Khuzestan province, including the 2018 attack, which the group had claimed responsibility for.

The execution comes amid ongoing tensions between Iran and the West over its nuclear program, as well as the detention of other prisoners with Western ties in Iran.

The Swedish Foreign Minister has condemned Cha’ab’s execution, describing the death penalty as “inhumane and irrevocable punishment.”