Syrian authorities reportedly arrested hundreds of protesters and dissidents Tuesday as the military surrounded several cities and villages, pro-democracy activists said.
Tuesday's move by the military came a day after at least 39 people were killed and 70 wounded in the restive southern city of Daraa after the army fired on demonstrators.
Telephone lines and water and electricity supplies were cut in most cities and villages in the southwestern Hauran region, where Daraa is located, activists from the Syrian Revolution 2011 group posted on Facebook.
There were mass arrests in Daraa as well as the cities of Duma and Homs, where uniformed men were seen attempting to enter a hospital where injured protesters were being treated.
Tanks and sharpshooters were seen throughout Daraa early Tuesday. Witnesses said earlier that snipers were shooting "at anything that moves."
The Syrian government says the troops were deployed to Daraa to quell a conspiracy by Islamists.
Meanwhile, the United States was considering further sanctions against the Damascus regime in the wake of the crackdowns, the White House said Monday.
At the United Nations, France, Britain, Germany and Portugal were reported to be drafting a text condemning the killings in Syria. These countries also support U.N. Secretary-General Ban Ki-moon's call for an independent, transparent investigation into the killings.
The U.S. also asked nonessential embassy personnel in Syria and family members to leave the country, and instructed its citizens to avoid all travel to Syria.
For more than a month, Syrian protesters have taken to the streets to demand greater freedoms and, increasingly, the ouster of President Bashar al-Assad and his Baath Party, which has ruled the country for nearly 40 years.
Human rights advocates said security forces have killed an estimated 400 people since the unrest began.
