Syrian Prime Minister Riyad Hijab has defected less than two months after taking office.
The news came shortly after Syrian state-run TV said that Hijab was fired from his post.
Mr Hijab's defection, if confirmed, is one of the most high profile desertions from President Bashar al-Assad's political and military circles.
Earlier reports said he was in Jordan with his family. However, Jordanian state TV have denied this.
On Sunday, al Arabiya television reported a senior Syrian intelligence officer had also defected to Jordan.
Mr Hijab, a Sunni Muslim from Syria's Sunni province of Deir al-Zor, was also a ruling Baath Party apparatchik.
Mr Assad had appointed Mr Hijab, a former agriculture minister, as prime minister in June following a parliamentary election which came after more than a year of violent protests against Mr Assad's rule.
State television said Omar Ghalawanji, who was a deputy prime minister as well as minister for local administration, would lead a temporary caretaker government.
The White House has said the defection of Syria's prime minister shows that President Bashar al-Assad has lost cohesion within his inner circle and is struggling to sustain a following among the Syrian people.
"This is a sign that Assad's grip on power is loosening," White House spokesman Jay Carney told a news briefing.
"The momentum is with the opposition and with the Syrian people."
TV station bombing
A bomb has exploded on the third floor of a Syrian state television and radio building in Damascus, state media has reported.
The television station, which continued broadcasting, carried an interview with Information Minister Omran al-Zoabi who said some employees were slightly wounded in the blast.
There were no deaths.
"There is a lot of damage," Mr Zoabi said.
"I'm in the ... radio and television building and everything is working and will continue to work. We have a lot of studios and equipment," he said.