Iranian media confirmed the incident, which took place on Thursday, but said that the men were armed, had been instigators of "riots", and were killed by security forces when they opened fire from their hideout in the western province of Kermanshah.

Brothers Meisam Visi and Mojtaba Visi, adherents of the Yarsan faith, had been living in hiding after the January protests, the Norway-based Hengaw rights group said.

The Yarsan faith is a fusion of other religions and beliefs that dates back to the 15th century.

The brothers were shot dead by Revolutionary Guards who surrounded their hideout early on Thursday in a village in the Dalahu district of the province and opened fire "without warning", Hengaw added.

The France-based Kurdistan Human Rights Network published a similar report, saying the pair had gone into hiding because of "fear of arrest".

But the Tasnim news agency described them as "two of the main instigators of the January riots in the Kermanshah region", and said they had opened fire on security forces.

"The security forces, acting within their legal mandate and in self-defence, returned fire, resulting in the deaths of the two armed terrorists," it added.

Iran was rocked this year by anti-government protests that peaked on the nights of January 8 and 9, before the US-Israeli war against the Islamic republic erupted on February 28.

Iranian authorities have described the protests as "riots" instigated by Israel and the United States.

However, rights activists have said thousands of innocent people were shot dead by security forces in a crackdown on legitimate protests.