Will Davies, a spokesman for Avaaz.org, said the group has received information that only 13 people have been released, The Daily Telegraph reported. Avaaz communicates with activists inside Syria.
"Making this promise to release more than 700 is another case of regime stalling tactics as the regime plays for time and tries to placate the Arab League," Davies said.
Syria agreed to a number of steps recommended by the Arab League in a plan to end the violence there. They also included withdrawing security forces from a number of cities that are centers of opposition to the government of President Bashar Assad.
The United Nations estimates 5,000 people have died, most of them dissidents killed by security forces, since large protests began in Syria.