Rebels seized an air defense facility and attacked a military airport in eastern Syria on Saturday, a monitoring group said, hitting back at an air force which President Bashar Assad is increasingly relying on to crush his opponents.
The attacks in eastern oil-producing Deir al-Zor province follow rebel strikes against military airports in the Aleppo and Idlib areas, close to the border with Turkey.
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Assad, battling a 17-month-old uprising in which 20,000 people have been killed, has lost control of rural areas in northern, eastern and southern regions and has resorted to helicopter gunships and fighter jets to subdue his foes.
The aerial bombardment has driven fresh waves of refugees into neighboring countries, reviving Turkish calls for "safe zones" to be set up on Syrian territory - appeals ignored by a divided UN Security Council and by Western powers reluctant to commit the military forces needed to secure such zones.
Rebels in Deir al-Zor overran an air defense building, taking at least 16 captives and seizing an unknown number of anti-aircraft rockets, said Rami Abdulrahman of the British-based Syrian Observatory for Human Rights.
Captives in Albu Kamal
Video posted on the Internet by activists showed the officers and soldiers captured by the rebel fighters as well as an arsenal of rocket-propelled grenades and heavy ammunition seized in the raid.
Abdulrahman said rebels also attacked the Hamdan military airbase at Albu Kamal, close to Syria's eastern border with Iraq, but did not succeed in breaking into it.
The attacks come three days after rebels said they had damaged several helicopters at the Taftanaz air base in Idlib province. The insurgents also said they have shot down a fighter jet and a helicopter last week.
Assad's forces have made numerous air strikes on civilians in rebel-held areas. Helicopters have strafed towns with heavy machineguns, and jets have unleashed rockets and bombs against opposition strongholds.
Bombardments of northern towns such as Azaz and Anadan, of which Assad lost control weeks ago, have led to thousands of residents fleeing to safety in Turkey.
Ankara made its call for safe havens inside Syria after the UN refugee agency said the flow of Syrians into Turkey and Jordan - which already host more than 150,000 registered refugees - was rising sharply.
But a ministerial meeting of the Security Council produced nothing beyond a French plan to channel more aid to rebel areas, an initiative which will do nothing to stem the flow of civilians fleeing the fighting.
Turkish government sources said Ankara would again push for agreement on safe zones inside Syria at the General Assembly later this month and would try to put pressure on Russia and Iran, which strongly oppose any such action.
Prime Minister Tayyip Erdogan, a former ally of Assad, showed his frustration at the lack of international action.
"We cannot take such a measure unless the United Nations Security Council decides in favor of it ... First a decision for the no-fly zone must be taken, then we would be able to take a step towards a buffer zone," Erdogan said in an interview broadcast on Turkish television late on Friday.
"Bashar al-Assad has come to the end of his political life. At the moment, Assad is acting in Syria not as a politician, but as an element, an actor, of war," he said.
Jordan said on Saturday it was "stretched to the limit" by the influx of refugees from southern Syria. The resource-poor kingdom of 7 million has accepted 70,000 registered refugees but says it is hosting 140,000 in local communities.
Planning Minister Jafaar Hassan said the influx was "reaching limits that the government cannot continue to shoulder", estimating the cost of sheltering the refugees at $230 million this year, rising to $285 million in 2013.
A United Nations official said 1,600 people were killed in Syria in the last week, the highest weekly figure in nearly a year and a half of conflict, and aid agencies say living conditions are worsening dramatically.
An estimated 1.2 million people are uprooted within Syria, including 150,000 in Damascus and surrounding areas, according to the United Nations.
UN Secretary-General Ban Ki-moon said he had pressed the Syrian government to allow in international aid workers, and received a positive reply during talks in Tehran this week.
Ban told Reuters he had "long and in-depth discussions with the Syrian officials" on the sidelines of a Non-Aligned Movement meeting. "While I criticized all the parties that have been depending on military means to resolve this issue, the primary responsibility rests with the Syrian government," he said.
But Russian Foreign Minister Sergei Lavrov said it would be wrong to press Damascus alone to end the violence.
"It is absolutely unrealistic to say that the unilateral capitulation of one of the parties in conflict is the only way out, in a situation when there's ongoing urban fighting," he told students of the Moscow Institute of Foreign Relations.