BEIRUT - Fighting between rebels and government forces raged near the Syrian capital Damascus on Monday, forcing an inbound commercial jet to turn back while the U.N. 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 al-Assad in fluent English, flew from Beirut to London. But it was not immediately clear whether he had defected.

The fighting over the last few weeks in and around Damascus has been the most serious in the capital since July, when rebels captured several neighborhoods 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 U.N.'s regional humanitarian coordinator for Syria.

Nouicer said the U.N. was withdrawing most of its international staff from Syria for security reasons, adding that up to one quarter of the 100 international staff working for several U.N. agencies could leave by week's end. There are about 900 more local staff working for the U.N. in Syria, officials said.

U.N. 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 canceled all further flights to Syria for Monday and Tuesday and will decide whether to resume flights later in the week, the officials said, speaking on condition of anonymity because they were not authorized to speak to reporters.

EgyptAir had just resumed flights after a three-day suspension because of violence near the airport.

Emirates airlines said on its website that all flights to Syria were suspended "until further notice."

The Britain-based opposition activist group Syrian Observatory for Human Rights said the clashes were within two miles of the airport, which is about 15 miles southeast of the city center.