Fighting between rebels and government forces raged near the Syrian capital Damascus, forcing an inbound commercial jet to turn back while the UN said it was withdrawing staff because of deteriorating security conditions.
Lebanese security officials said Jihad Makdissi, a polished Foreign Ministry spokesman known for defending the regime of President Bashar Assad in fluent English, flew from Beirut to London. But it was not immediately clear whether he had defected.
The fighting over the past few weeks in and around Damascus has been the most serious in the capital since July, when rebels captured several neighbourhoods before a swift government counteroffensive swept them out.
The spike in violence recently is concentrated in the ring of mostly poor suburbs around Damascus but often bleeds into the capital itself as rebels bring their fight closer to Assad's seat of power.
Assad's forces have so far repelled major rebel advances on the capital, though their hold may be slipping.
"The security situation has become extremely difficult, including in Damascus," said Radhouane Nouicer, the UN's regional humanitarian coordinator for Syria.
Nouicer said the UN was withdrawing most of its international staff from Syria due to security issues, adding that up to one quarter of the 100 international staff working for several UN agencies could leave by week's end.
There are about 900 more local staff working for the UN in Syria, officials said.
UN teams are also stopping most staff trips outside Damascus. In another sign of deteriorating security, an Egyptian commercial jet aborted a trip to Damascus in mid-flight because of violence near the airport.
The EgyptAir flight from Cairo rerouted about 30 minutes after takeoff because Egyptian officials received word from their counterparts in Damascus that the area near the airport was not safe, Egyptian airport officials said.
EgyptAir cancelled all further flights to Syria yesterday and today and will decide later whether to resume flights later in the week, the officials said, speaking on condition of anonymity because they were not authorised to speak to reporters.