Syria's rebels stepped up attacks on strategic sites including a sprawling military complex in the country's north, while reports emerged that President Bashar Assad's forces continued to fire Scud missiles at rebel areas.
Russian President Vladimir Putin told European leaders that Russia does not seek to protect Mr Assad but that only a negotiated solution can end the conflict - an outcome which looks unlikely as rebels make gains across the country.
While few observers expect Syria's 21-month-old conflict to end soon; most say steady rebel advances appear to be tipping the balance in favour of those fighting to topple the Assad regime.
Anti-regime activists reported rebel attacks on strategic government sites in northern Syria, showing rebel efforts to cut government supply lines, free up roads and seize arms from government bases.
Near the northern city of Aleppo, rebels clashed with government forces at a sprawling military complex by the town of Al-Safira, activists said. An activist in the town said the complex contains military factories, a scientific research centre that produces chemical weapons as well as an air defence and an artillery base.
Rebels seized the artillery base earlier this week and have been trying to seize the air defence base, said Hussein, who gave only his first name for fear of retribution.
The town's proximity to the facilities has cost it dearly, he said. Government air strikes often target civilian areas, and more than two-thirds of the town's residents have fled, fearing the regime will use chemical weapons.
"We are scared that they will be blown up or that the regime will use them in revenge on the town," he added.
Bilal Saab, head of the Institute for Near East and Gulf Military Analysis, confirmed that the Al-Safira complex houses a chemical weapons production facility but said it is unclear if such weapons have been stored there ready for use, or if rebels would even be able to use such weapons.
The Britain-based Syrian Observatory for Human Rights said seven rebels were killed in clashes in the area. It said nearly two dozen more died in a government air strike earlier this week after they captured a military warehouse. Activists also said rebels had launched attacks on a number of military targets near the central city of Hama.