Riad Seif was detained along with at least five members of the Kurdish Democratic Progressive Party during a sit-in near a Damascus government building, said a statement by the Syrian Organization for Human Rights.

Security forces beat and then detained some of the demonstrators, after three of those taking part in the sit-in attempted to deliver a message to Prime Minister Naji Otri, said human rights lawyer Anwar Bunni, adding that several demonstrators had been wounded.

The rights group also said some demonstrators had been wounded, and expressed its "concern over the violent behavior of security services toward peaceful protestors who are asking for the release of political detainees."

Bloody clashes, initially sparked by a riot between rival fans at a football match, pitted mainly Kurdish protestors against security forces and Arab tribesmen in the northern Syrian towns of Qameshli and Aleppo in March 2004.

Forty people were killed during several days of violence according to Kurdish sources, though Syrian authorities said 25 people had died.

Seif, 54, had been released in January after nearly five years in prison for participating in a short-lived "Damascus spring" of liberalization in 2001 by President Bashar al-Assad.

He was briefly rearrested last month after serving time on charges of working "to change the constitution through illegal means."