Damascus - Syrian Prime Minister Riad Hijab announced he was joining the rebels on Monday after slipping across the border into Jordan during the night in the highest-ranking defection of the nearly 17-month uprising.
Hijab was one of the leading Sunni Muslims in President Bashar Assad's minority Alawite-dominated regime.
He accused his former master of carrying out a "genocide" against his own people but said four decades of Assad family rule were collapsing.
"I announce my defection today [Monday] from the regime of killing and terror, and I join the ranks of the revolt," Hijab said in statement read by his spokesperson Mohammed al-Otri on Al-Jazeera news channel from Amman.
"Syria is passing through the most difficult war crimes, genocide, and barbaric killings and massacres against unarmed citizens," he said.
Hijab's home province of Deir Ezzor in the northeast has been one of the key battlegrounds of the conflict and seen a mounting death toll from operations by the army in recent weeks.
Life on line
Otri said the premier's defection took "months" to organise and "rebels inside the country have secured this honourable exit for him".
"He put his life on the line for this revolt... to tell the world that we were forced to be with this regime and the sword was at our necks," the spokesperson said.
"Our information is confirmed through Riad Hijab that the Syrian regime is collapsing and will definitely fall."
Otri said the premier was in a "safe haven" with his family and "will soon appear and talk".
The Syrian opposition in Jordan said that Otri and his family had slipped over the border during the night accompanied by two government ministers and three army officers.
"The Free Syrian Army helped all of them cross the border. They are now in a safe place inside the kingdom. Several other army officers defected and arrived in Jordan last night," said Syrian National Council member Khalid Zein al-Abedin.
Another opposition member in Jordan said: "The opposition and the Free Syrian Army are coordinating now to help more army officers and officials defect to Jordan in the coming few days."
'Beginning of end'
The opposition SNC hailed a new blow to Assad, who has already seen no fewer than 31 of his generals cross into Turkey to join the rebellion and a growing number of his ambassadors break ranks.
"This defection shows that the regime is disintegrating. It is the beginning of the end," its leader Abdel Basset Sayda said.
In a statement, the SNC renewed its call to officials still loyal to Assad's regime to defect.
"There are no more excuses to stay on board the criminal regime's ship," it said. "It is time to choose between loyalty to Syria and its people, or to a murderous, terrorist gang, whose hour of reckoning and punishment is nigh."
In Damascus, state television put out a terse report announcing that Hijab had been dismissed. It said Deputy Prime Minister and Local Government Minister Omar Ghalawanji had been appointed caretaker premier.
The 46-year-old Hijab was only appointed on 6 June following a widely boycotted 7 May parliamentary election that was hailed as a centrepiece of reform by the Assad regime but dismissed as a farce by Arab and Western governments.
Major ground assault
An agricultural engineer by training, he was agriculture minister under his predecessor Adel Safar who was appointed in April 2011, shortly after the outbreak of the uprising.
Word of his defection came as the army readied a major ground assault against rebels in commercial capital Aleppo, who say they control half of the city of some 2.7 million people.
They also came as a bomb blast rocked Syrian state television headquarters in the heart of Damascus, wounding several people just two days after the army said it had seized the last rebel-held area of the capital.
The morning bombing struck management offices on the third floor of the television building in the heavily protected Omayyad district of the city.
"It is clear that the blast was caused by an explosive device," said Information Minister Omran al-Zoabi. "Several of our colleagues were injured, but there were no serious injuries, and no dead."
In Aleppo, the army bombarded a string of rebel neighbourhoods after government security officials said that troops had completed their build-up and that a 20 000-strong force was poised for a ground assault.
A rebel commander was killed in the Salaheddin district in the southwest, and troops shelled the Palace of Justice as well as the Marjeh and Shaar districts, the Syrian Observatory said.
A total of nine people were killed in Aleppo early on Monday, among them eight civilians, the watchdog said.
A senior security official said on Sunday that the army had completed its deployment of reinforcements to Aleppo, ready for a decisive showdown.
"All the reinforcements have arrived and they are surrounding the city," the official said. "The army is ready to launch its offensive, but is awaiting orders."
Elsewhere in Syria, the Observatory reported another 19 deaths early on Monday - 13 civilians and six rebels.