The independent organization said it had received reports that at least 20 people had been killed in Deraa since tanks moved in on Monday, but communications with the southern town where the protests against President Bashar al-Assad began on March 18 had been cut making it hard to verify the information.

At least 500 were arrested elsewhere in Syria, Sawasiah said.

Amnesty international, citing sources in Deraa, said at least 23 people were killed when tanks shelled Deraa.

Government forces also stormed the Damascus suburbs of Douma and Mouadhamiya on Monday, shooting and making arrests, a day after they swept into the coastal town of Jabla, where at least 13 civilians were killed, according to rights campaigners.

Diplomats said the figures for civilians killed could reach up to 50 in Deraa and 12 in Mouadhamiya, which lies on the road to the occupied Golan Heights southwest of Damascus.

Reuters