"Syria's uprising is screaming with 200 martyrs, hundreds of injured and a similar number of arrests," the Damascus Declaration group said in a letter sent on Monday to the secretary general of the Arab League.
Syrian protesters last month began demonstrating in the southern city of Deraa last month to call for increased freedom of expression and assembly and an end to corruption.
"The regime unleashes its forces to besiege cities and terrorise civilians, while protesters across Syria thunder with the same chant - 'peaceful peaceful'," - it said.
"We ask you to... impose political, diplomatic and economic sanctions on the Syrian regime, which continues to be the faithful guardian of Hafez al-Assad's legacy," the letter said,
Human Rights Watch said 27 people were killed on Friday in Deraa and condemned the country of preventing injured protesters from reaching hospitals for medial treatment.