Those detained in the northeastern town of Kamishli were identified as Yakiti officials Hassan Saleh, Maaruf Mala Ahmd and Muhammad Mustapha, and artist and activist Anuar Nasso, said the London-based Syrian Observatory for Human Rights.

"The four Kurds were summoned by the head of the region and were then arrested for unknown reasons," it said in a statement.

Yakiti had adopted a resolution earlier this month advocating "a solution to the Kurdish issue in Syria, through the self-determination of Syrian Kurdistan."

The rights group appealed to the Syrian authorities "to free the four detained Kurds and all prisoners of conscience in Syria," and "to pass a law that recognises the activities of political parties and civil society, which guarantee the integrity and unity of the country."

More than 1.5 million Kurds live in Syria, comprising nine percent of the population. They have long sought official recognition of the Kurdish language and culture.