"Ismail Mustafa was summoned by the security services in Aleppo on Saturday and then he was arrested for no apparent reason," a statement said.

"We express our deep concern over this measure which is contrary to human rights," said the statement signed by the London-based Syrian Observatory for Human Rights, the National Organisation of Human Rights in Syria and the Syrian League for the Defence of Human Rights.

The rights watchdogs also accused Syrian authorities of having "intensified arbitrary detention recently" and said such acts threaten freedoms.

They also urged the authorities to immediately release Mustafa "or give him a fair trial."

Human Rights Watch issued a damning report of Syria's handling of its Kurdish minority in November, accusing Damascus of being "especially hostile to any Kurdish political or cultural expression."

The New York-based watchdog also documented the arrests and trials of at least 15 prominent Syrian Kurdish political leaders since 2005.

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.