The demonstration in the northeastern town of Qamishli had demanded an independent inquiry into the death of rights campaigner Sheikh Maashuk Khaznawi, the National Organisation of Human Rights in Syria (NOHRS) said.

Khaznawi vanished on May 10, 2005, and the government announced on June 1 that he was dead, triggering the protest on June 5. The 50 people were arrested at the rally and held for two months before being released on bail.

The protesters were sentenced on Sunday on charges of "inciting religious and racial dissent and conflict with different religions and groups of the nation," the NOHRS said.

NOHRS president Ammar Qorabi said he hoped that "these citizens will be found innocent if they launch an appeal against the ruling," pointing to the fact that "the Syrian constitution allows for peaceful demonstrations."

The 2005 rally had called for the establishment of a independent commission including Kurdish lawyers to probe Khaznawi's death.

The authorities later said they had arrested two members of a "criminal gang" of five they said were responsible for killing the popular Khaznawi, 46, who was vice president of a centre for Islamic studies in Damascus.

Khaznawi was a fervent defender of Kurdish human rights and a critic of Syria's treatment of Kurdish people.

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 their culture.