International envoy for Syria Lakhdar Brahimi was Friday in talks with top diplomats from Russia and the United States in Geneva, as opposition activists said rebels, fighting to oust President Bashar al-Assad, captured a major air base.
The aim of the Geneva talks, the second since December 9, was to bridge differences between Russia and the US on how to end Syria's nearly two-year conflict.
The US wants al-Assad to step down, while Russia says it is a matter for Syrians to decide.
The meeting was being attended by Brahimi, Russian Deputy Foreign Minister Mikhail Bogdanov and US Deputy Secretary of State William Burns.
Earlier this week Brahimi said he did not see al-Assad as part of the transitional government that was outlined in a plan agreed to by major powers and Arab countries in Geneva last year.
Meanwhile, the opposition Syrian Observatory for Human Rights said rebels, led by the Jihadist al-Nusra Front, had taken full control of the strategic Taftanaz military airport in the northern province of Idlib after weeks of fighting against government troops.
"The fighters are now controlling all the facilities of Taftanaz airport," Rami Abdel-Rahman, the head the observatory, told dpa.
"The regime forces have left behind prisoners and dead bodies in Taftanaz."
The air base is the largest to be captured by rebels since the revolt against al-Assad's rule started in March 2011, said theBritain-based observatory.
Footage videos posted online by activists showed what they called Islamist fighters inspecting armoured vehicles outside the air base's main gate and an ammunition store inside Taftanaz, which is the government's biggest military airport in the north.
The opposition said al-Assad's troops used Taftanaz to pound rebel-held areas in the north.
Insurgents broke into the air base Wednesday night, and by Friday morning seized full control of the facility, which also served as a base of supplies for government forces.
The airport is located near a road linking the capital Damascus and Aleppo, Syria's biggest city.
Syria's state television denied claims that the sprawling facility had fallen to rebels, saying that government troops had repulsed an attack by "terrorists" on the air base.
"Guards in Taftanaz inflicted heavy losses on the terrorists, killing and injuring a number of them, while the rest fled," the broadcaster reported.
News from Syria is hard to verify as authorities have barred most foreign media from the country since the revolt started.
The number of Syrians, who have fled to neighbouring countries and North Africa, has jumped by more than 100,000 in the past month to over 600,000, the UN refugee agency said Friday.
The UN High Commissioner for Refugees (UNHCR) added that as of Thursday, 612,000 Syrians had been counted.
UNHCR spokesman Adrian Edwards said the harsh winter weather in the region was bringing new hardship to the refugees.
In Jordan, "many of those arriving have been barefoot, with their clothing soaked and covered in mud and snow," he added.
Saudi Arabia said it would offer 10 million dollars to provide urgent relief assistance for the Syrian refugees, reported the state news agency SPA.
Syria's 21-month conflict has claimed the lives of more than 60,000 people, according to UN estimates.