US President Barack Obama has condemned an "abhorrent" crackdown in Syria which killed 24 demonstrators and any violence by protesters following reports of deaths among security forces.
"I strongly condemn the abhorrent violence committed against peaceful protesters by the Syrian government today and over the past few weeks," Obama said in a written statement, the latest in a flurry of US rebukes of Damascus.
"I also condemn any use of violence by protesters.
"I call upon the Syrian authorities to refrain from any further violence against peaceful protesters."
Obama also called for an end to arbitrary arrests, detention and torture of prisoners and said the Syrian authorities should allow independent verification of recent political unrest in the country.
The head of Syria's National Organization for Human Rights said that at least 24 protesters were killed yesterday as anti-regime demonstrations and clashed with security forces raged around Syria.
The official SANA news agency said 19 members of the security forces were killed and 75 were wounded by "armed groups" in the southern town of Daraa.
President Bashar al-Assad, under popular pressure to introduce major political reforms and end emergency powers which give security services great leeway to crush dissent, had ordered a probe into previous protest casualties in Daraa.
The agricultural city of Daraa has been the focal point of anti-government protests marred by deadly violence that human rights activists blame on the security services and the government blames on "armed" groups.