Syrian rebels say they have seized an air defence facility and an airport in the east of the country, while the government claims it has fought off an offensive on another airbase in Aleppo.
The attacks in the oil-producing Deir al-Zor province come as part of an apparent strategy change by rebels who are now prioritising Syrian air force assets.
The Syrian Observatory for Human Rights says rebels seized several anti-aircraft rockets.
Amateur video purportedly shows fresh shelling by government forces in Homs, the nerve-centre of the uprising.
Other footage, said to have been filmed on Saturday, shows much of the northern town of Azaz reduced to rubble. Activists there claim they have been subjected to almost daily attacks by the Syrian regime.
The ongoing violence continues to force thousands of residents to flee to the Turkish border.
Ankara has temporarily closed its checkpoint at Bab al-Salam as it struggles to cope with an influx of around 80,000 refugees. Turkey says it will open four more camps by next week.
On Saturday, the Syrian government freed more than 200 detainees from police stations in Damascus, Aleppo and Homs.
The groups had apparently been involved in anti-government activities but it is not clear if any were members of the Free Syria Army.
Prisoners signed declarations that they would not rejoin the uprising.
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