Sawasiah, founded by jailed Syrian human rights lawyer Mohannad al-Hassani, also said thousands of Syrians have been arrested and scores have gone missing after demonstrations demanding political freedoms and an end to corruption began almost six weeks ago.
"We call on civilised governments to take action to stop the bloodbath in Syria and to reign in the Syrian regime and halt its murders, torture, sieges and arrests. We have the names of at least 500 confirmed killed," Sawasiah said in a statement sent to Reuters.
"The regime continues its organised campaign of killings against its own people with impunity. The shelling of Deraa is a crime against humanity," the statement said, referring to the army using tanks to crush resistance in the city of Deraa, where the protests began. (*)