The US state department said today it was disturbed by reports of a Syrian military operation in Deraa including the use of tanks and the arbitrary arrest of young men, calling these "barbaric measures."
"These are, quite frankly, barbaric measures and they amount to the collective punishment of innocent civilians," state department spokesman Mark Toner told reporters.
Meanwhile, the Red Cross called on Syria today to allow health workers safe access to people injured in bloody protests, especially in the southern city of Deraa, and let it visit those who have been arrested.
The independent humanitarian agency said Syrian authorities were close to letting it and the Syrian Red Crescent into rural hospitals around the capital Damascus in the coming days.
But it was vital to reach Deraa, cradle of the pro-democracy demonstrations, where many casualties have been reported, the International Committee of the Red Cross (ICRC) said. Even the Syrian Red Crescent has not been allowed into Deraa, it said.
"So far we have had restricted access, limited access to certain areas. However today we need to have larger access, especially in the south, and here I talk about Deraa," ICRC spokesman Hisham Hassan told a news briefing in Geneva.
In the old quarter of Deraa, shelled and machine-gunned into submission on Saturday, security forces forced their way into houses on Sunday and took away many men under 40, witnesses said by telephone.
Meanwhile Britain said today it was working with its European partners on targeted sanctions on Syrian officials.
"We are now working with our European partners on targeted sanctions, on asset freezes and travel bans. I will be discussing those further with the French foreign minister this evening," foreign secretary William Hague told the British parliament.
At least 560 civilians have been killed by president Bashar al-Assad's security forces since the Deraa uprising erupted on March 18th, human rights groups say.
The ICRC said it had delivered medical supplies to some hospitals. Medics have been working hard to provide first aid and evacuate victims in some areas, but they must be able to carry out their work in safety and ambulances must be respected.
"It is urgent that emergency medical services, first-aid workers and others performing life-saving tasks swiftly reach those in need," Marianne Gasser, head of the ICRC delegation in Damascus, said.
All those arrested and detained must be treated humanely and held in decent conditions, the ICRC said. Its confidential reports on prison visits are given only to the detaining authorities.
"We want to visit those detained in connection with the current violence but also detainees being held generally in Syria, as we do elsewhere in Tunisia, Jordan, Lebanon and Libya," Mr Hassan said.