Syria: US condemns 'brutality and violence'
The White House said the government was leading Syria down a "dangerous path" and called for "an immediate end to the brutality and violence".
At least 28 people were killed in fresh clashes in Idlib province on Friday.
The violence came as government forces moved on the town of Jisr al-Shughour where the government said 120 security personnel had been killed.
Hundreds of civilians have fled north into Turkey to escape the assault.
Assad 'unavailable'
In a statement, White House spokesman Jay Carney repeated calls for the Syrian security forces to exercise restraint, and said the US stood by those Syrians who were "demanding dignity and the transition to democracy that they deserve".
"The Syrian government is leading Syria on a dangerous path," he said.
"For that reason, it is critical that all Syrians remain united, work to prevent sectarian conflict, and pursue their aspirations peacefully."
UN Secretary General Ban Ki-moon also expressed concern over the high civilian toll, describing the use of military force as "unacceptable".
A spokesman for Mr Ban said he was "keen to speak to" Syrian President Bashar al-Assad, but that the president has repeatedly been "unavailable" in recent days.
Syria has prevented foreign journalists, including those from the BBC, from entering the country, making it difficult to independently verify reports from there.
But anti-government activists said about 15 people died in the northern province of Idlib on Friday, most of them in Maarat al-Numan where tanks and helicopters fired on protesters who had taken to the streets after prayers; Kazinform cites BBC News.
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