An Iranian Kurdish dissident was shot dead while walking home in Istanbul, Turkish media reported on Wednesday, in what rights groups described as a political assassination.

Masoud Nazari — known for his criticism of Iran‘s clerical establishment and military, was attacked by an unidentified gunman in the Arnavutkoy district at around 1730 GMT on Tuesday, according to the private DHA news agency. The assailant fled the scene.

Nazari sustained serious injuries and later died in hospital, the reports said.

He had moved to Istanbul a decade ago due to his opposition to the Islamic republic, said the Haalvsh rights group, which is based outside Iran and specialises in issues of the country’s Sunni minority, and the Norway-based Hengaw, which focuses on Iranian Kurds.

They said in separate statements that Nazari was a member of Iran’s Sunni Kurdish minority from the city of Javanrud in the northwestern province of Kermanshah, which has a large Kurdish population.

He was a well-known figure in Kurdish Sunni religious circles and a strong critic of the religious policies in Iran’s Shiite-ruled theocracy, Haalvsh said. It quoted an unnamed family member as saying he had previously been threatened by Iranian security services.

“The assassination of Masoud Nazari is another example of the Islamic republic’s targeted attacks against political and religious activists abroad,” Hengaw said.

Turkish authorities have launched an investigation into the killing, local media reported.