Two people were killed in a shooting attack at a Shiite mourning ceremony in Iran late Friday night. Two other people were also wounded after the assailants opened fire at the worshipers from a car with no license plate, local media reported.

The incident took place during the Shiite religious festival of Ashura in the town of Dezful in the southwestern Khuzestan province that borders Iraq. The region, which has a significant ethnic Arab community, has been targeted in many armed attacks in recent years, Agence France-Presse (AFP) reported, citing Iran’s official IRNA news agency.

“It's not still clear whether the attack was a terrorist one,” AFP quoted provincial police official Col. Rahman Mousavi as saying. “Investigators are reviewing the matter and will announce the results as soon as possible.”

The two Iranians, who were killed during the attack, were Hossein Karimi Yeganeh, 28, and Bahman Rezaie, 25. The two wounded people were taken to hospital, Reuters reported, adding that no group has so far claimed responsibility for the attack.

Ashura is a 10-day festival of mourning, marking the assassination of Imam Hussein, a Shiite leader and the grandson of the Prophet Mohammed. Hussein was killed by the army of the Caliph Yazid shortly after the Islamic schism in 680 AD, an event that is linked to Islam's division into Shiite and Sunni sects.

In a similar attack that took place at a Shiite gathering in Saudi Arabia on Friday night, five people were killed and nine were injured by a gunman. A group claiming links to the Islamic State group, also known as ISIS, reportedly took responsibility for the attack.