Robert King / AP
In this image made from video and accessed Saturday, a Free Syrian Army fighter fires his weapon at a Syrian Army position through a hole in an empty and destroyed home during fighting in Aleppo, Syria.
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.
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 latest violence shows that government troops are still struggling to clear the city of lightly-armed rebel forces nearly five weeks after they stormed their way into it.
President of the Security Council Laurent Fabius and William Hague, Foreign Secretary of the United Kingdom, hold a joint press conference on the situation in Syria.
Another activist group, the Local Coordination Committees, said the government was making heavy use of warplanes in attacking rebel areas.
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 U.N. 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.
Activist video posted on the Internet showed the officers and soldiers captured by rebel fighters as well as an arsenal of rocket-propelled grenades and ammunition seized in the raid.
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 carried out 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 U.N. 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.
Rebels in Syria claim new video shows their forces shooting down an Army helicopter as it was bombarding a Damascus neighborhood. TODAY's Natalie Morales reports.
An estimated 1.2 million people are uprooted within Syria, including 150,000 in and around Damascus, the U.N. said.
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