Syrian authorities are holding in custody 20 opposition activists, a Syrian human rights group said Monday. The National Human Rights Organization in Syria said in a statement made available to The Associated Press in Damascus that authorities summoned and detained about 30 members of the "Damascus Declaration" group on Sunday and Monday. The group had held a conference December 1, the statement said. Ammar Qurabi, head of the rights group, said that 10 of those detained were released shortly after questioning, leaving 20 still in detention. Although Qurabi released the names of the 20 detainees, none were widely known.