Syria's prime minister has defected to neighbouring Jordan as government forces prepare for a major ground assault against rebels from Aleppo, the country's biggest city.
The move by Riyad Hijab marks one of the highest profile desertions from the Damascus government.
Syrian state television said Mr Hijab had been fired, but an official source in the Jordanian capital Amman said he had been dismissed only after he fled across the border with his family.
"I announce today my defection from the killing and terrorist regime and I announce that I have joined the ranks of the freedom and dignity revolution," Hijab said in a statement read in his name by the spokesman, which was broadcast on Al Jazeera television.
"I announce that I am from today a soldier in this blessed revolution."
Syrian state television reported Mr Hijab's dismissal as government forces appeared to prepare a ground assault to clear battered rebels from Aleppo, the country's biggest city.
"Hijab is in Jordan with his family," said the Jordanian official source. The source said Mr Hijab had defected to Jordan before his sacking.
The opposition Syrian National Council said a further two ministers and three army generals had defected with Hijab. That assertion could not immediately be verified.
The White House has said the defection of the prime minister showed that President Bashar al-Assad's government was "crumbling from within" and it repeated its call for him to step aside and end the violence gripping the country.
"This is a sign that Assad's grip on power is loosening. If he cannot maintain cohesion within his own inner circle, it reflects on his inability to maintain any following among the Syrian people that isn't brought about at the point of a gun," White House spokesman Jay Carney told a news briefing.
"The momentum is with the opposition and with the Syrian people. It's clear that these defections are reaching the highest levels of the Syrian government and Assad cannot restore his control over the country because the Syrian people will not allow it," he said.
Mr Hijab was a top official of the ruling Baath party but, like all other senior defectors so far from the government and armed forces, he was also a Sunni Muslim rather than a member of Assad's Alawite sect, which has long dominated the Syrian state.
President Bashar al-Assad appointed Mr Hijab, formerly agriculture minister, as prime minister only in June following a parliamentary election which authorities said was a step towards political reform but which opponents dismissed as a sham.
Mr Hijab's home province of Deir al-Zor has been under heavy Syrian army shelling for several weeks.
Syrian television said Omar Ghalawanji, who was previously a deputy prime minister, had been appointed to lead a temporary, caretaker government.
Earlier in the day, a bomb blast hit the Damascus headquarters of Syria's state broadcaster as troops backed by fighter jets kept up an offensive against the last rebel bastion in the capital.
The bomb exploded on the third floor of the state television and radio building, state TV said. However information minister Omran Zoabi said none of the injuries was serious, and the channel continued broadcasting.
Syrian army tanks shelled alleyways in Aleppo where rebels sought cover as a helicopter gunship fired heavy machineguns.
Snipers ran on rooftops targeting rebels, and one of them shot at a rebel car filled with bombs, setting the vehicle on fire.
Women and children fled the city, some crammed in the back of pickup trucks, while others walked on foot, heading to relatively safer rural areas.
Rebel commanders say they anticipate a major Syrian army offensive in Aleppo and one fighter said they had already had to pull back from some streets after army snipers advanced yesterday under cover of the fierce aerial and tank bombardment.
Reuters