Syrian charge d'affaires to Cyprus Lamia al-Hariri has defected, becoming the second diplomat to leave her post in July, Al Jazeera has learned.
Al-Hariri's defection on Tuesday comes just weeks after Nawaf Fares, the ambassador to Iraq, quit his post.
Tuesday's defection deals a harsh blow to the Syrian government as the regime battles a near 17-month-old uprising.
In an interview with Al Jazeera, Bassam Imadi, a former Syrian ambassador to Sweden, said that Hariri's defection is also significant because she is the niece of Farouk al-Sharaa, Syria's vice-president.
| Syrian rebels near Aleppo city, as they took much of the formerly loyalist city from the government [EPA]
"It must be very embarrassing to the regime that one of his [Sharaa's] closest officials is defecting," he said.
Imadi added that other Syrian ambassadors, including the envoys to Germany, the Czech Republic, and Belarus, had defected, but have not announced it publicly due to fears over government reprisals.
Another top defector, Brigadier General Manaf Tlass, called on Tuesday for the Syrian military to denounce what he described as crimes committed by President Bashar al-Assad's forces.
"I address you...as one of the Syrian Arab Army's sons who reject the criminal behaviour of this corrupt regime. The honourable people in the military would not accept these crimes," Tlass said in a televised statement on al-Arabiya television.
Tlass, a friend of Syrian President Bashar al-Assad and a son of a former defence minister, said that Syrians should work together to build a new, democratic country.
It was his first public appearance since he left Syria earlier this month. His long silence raised questions about whether he had joined the anti-Assad uprising or merely fled the civil war.
Aleppo under fire
Meanwhile, Syrian army helicopters fired rockets and machineguns near central Aleppo on Tuesday as they battled rebels trying to enlarge their foothold in the country's second city, forcing residents to flee.
Residents said fighter jets were flying over some rebel-held neighbourhoods, and that helicopters were firing at eastern and southern districts located around only 3km east of Aleppo's ancient citadel in the city centre.
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"I heard at least 20 rockets fired, I think from helicopters, and also a lot of machinegun fire," said a resident near one of the areas being shelled, who asked only to be identified by his first name Omar.
"Almost everyone has fled in panic, even my family. I have stayed to try to stop the looters, we hear they often come after an area is shelled," he added.
The bombing came as Hillary Clinton, the US secretary of state, insisted there was still time for Assad to hand over power, stressing the pace of events in Syria was speeding up.
"We do believe that it is not too late for the Assad regime to commence with planning for a transition to find a way that ends the violence," she told reporters, adding that things were "accelerating inside Syria".
The Arab League, meeting in Qatar on Monday, called on Assad to quit, but Syrian officials dismissed the bloc's call saying it was "hypocritical" and that some members of the league were backing the rebels.
In Aleppo, government forces were also seeking to quell a mutiny in the city's central prison, where eight people were killed, the Syrian Observatory for Human Rights said.
The rebel Free Syrian Army (FSA) described the mutiny as "the first step towards the liberation" of Aleppo.
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Elsewhere in the country, the Local Co-ordination Committees, a network of opposition activists, reported renewed shelling in parts of Damascus, including in the Barzeh district where the neighbourhood's mosque was reported damaged by intense shelling.
The army pushed into dissident districts in the south, entering the Kaddam and al-Assali areas where they carried out raids and arrests, according to the Observatory.
Many Damascus residents remain displaced by the recent fighting and were in need of humanitarian assistance, the International Commission of the Red Cross (ICRC) said.
"Although the situation has calmed down in some parts of the city, life is not back to normal," said Marianne Gasser, the ICRC's head of delegation in Syria.
"People who have fled their homes only want to be able to go back. Unfortunately, for many, there has not yet been any opportunity to do so."
The Local Co-ordination Committees said 150 people were killed across the country on Tuesday, including rebels.