BEIRUT, Lebanon - A prominent Syrian dissident, who the United States had urged be allowed to travel abroad for cancer treatment, has been arrested, a Syrian human rights group said Tuesday.
Riad Seif, a former member of Syria's parliament, was taken into custody Monday evening, the National Organization for Human Rights in Syria said in a statement.
The statement, e-mailed to The Associated Press, said a warrant for Seif had been issued for his participation in a December meeting of dissidents.
There was no official confirmation of the arrest from the Syrian government, which rarely comments on security measures against activists.
Syria had previously banned Seif from travel, a measure regularly taken against dissidents. Last summer, the U.S. State Department urged Syrian authorities to allow him to leave the country to receive medical treatment for prostate cancer.
In Washington, the State Department called for Seif's immediate release. The arrest was "yet another example of the Syrian regime's contempt for the universally recognized right of free expression of ideas, and its blatant attempts to silence and intimidate the Syrian people," deputy spokesman Tom Casey said.
Seif, who has spent time in jail for criticizing President Bashar Assad's government, told the AP in December that refusing to allow him to seek treatment abroad was "like being sentenced to a slow death."
In the past year, six prominent government critics and human rights campaigners have been convicted and sentenced to up to 12 years in prison. Among them are prominent lawyer Anwar al-Bunni and one of Syria's most respected writers, Michel Kilo.
Human rights groups say Syria is holding hundreds of political prisoners and activists, some without charge or trial.
Seif is head of the secretariat of the Damascus Declaration group, made up of five small opposition groups and six political figures who say they want to build internal support for peaceful democratic change in Syria.
Authorities arrested several members after it held a December meeting.
President Bush recently criticized the detentions as an example of the Syrian government's continued repression of its people.
Associated Press Writer Matthew Lee in Washington contributed to this report.