Syrian rebels have captured an air defence base east of Aleppo as government forces battled fighters on several fronts across the country, activists say.
The air defence base seized by the rebels was located in al-Tana village by the Koris military airport on the road east from Aleppo to al-Raqqa, the Syrian Observatory for Human Rights said on Friday.
Clashes were also taking place at a military barracks close to Maarat al-Nuaman, a town on the main highway to the
northwestern city of Aleppo, which was seized by rebel forces earlier this week, the Observatory said.
The pro-opposition Observatory said rebels had gone on the offensive killing more than 100 soldiers in two days.
Fourteen soldiers died in an attack on an army post in the southern province of Daraa on Friday, it said, a
day after the army suffered 92 losses, the highest daily total for the military of the 19-month conflict.
The Britain-based watchdog gave a death toll for Thursday of more than 260 people, including civilians and fighters on both sides in violence in the capital and the north, west and east.
The official SANA news agency also reported fighting nationwide and said dozens of rebels, which it called "mercenary terrorists", had been killed.
The reports could not be independently verified but they indicate a rapidly intensifying conflict, with the death tolls of the past several weeks far exceeding previous months.
Meanwhile, Russia said on Friday that no weapons were aboard a Syrian civilian jet grounded by Turkish authorities on Wednesday and the plane had been carrying a legal shipment of radar equipment.
"We have no secrets." Foreign Minister Sergei Lavrov said.
"There were, of course, no weapons on the plane and could not have been any. There was a cargo on the plane that a legal Russian supplier was sending in a legal way to a legal customer," he told Russian state television.
Recep Tayyip Erdogan, Turkey's prime minister, said on Thursday that the plane forced to land in Ankara en route from Moscow to Damascus on Wednesday, and later released, had been carrying Russian-made munitions destined for Syria's armed forces.
Lavrov said the cargo in question was "electro-technical equipment for a radar station", adding that it was of dual military-civilian use but was "not prohibited by international conventions".
"Shipping such a cargo on civilian aircraft is an absolutely normal practice," he said.
International attention has focused on the Turkish border in the past week. Turkey scrambled two fighter planes to the border with Syria on Friday after a Syrian military helicopter bombed the Syrian border town of Azmarin.
Elsewhere, Aleppo and the city of Homs - north of Damascus and near the border with Lebanon - are being fought over and clashes take place almost daily in the suburbs of the capital Damascus as well as in the countryside.
SANA said government forces were mounting operations to clear Aleppo's Karm al-Jabal area of rebels on Friday.
Aleppo, Syria's largest city and commercial hub, has been contested since July. The rebel capture of Maarat al-Nuaman cut the highway between Aleppo and Homs, the main route for the government to resupply and reinforce the northern city.
Aleppo's main hospital has also been overwhelmed with casualties, with many of those injured in the fighting being children, activists said.
There were also small, peaceful protests held in Idlib province, following Muslim prayers on Friday. Demonstrators there again called for the downfall of al-Assad's regime.
More than 30,000 people have been killed in the conflict which started out as a popular uprising against four decades of Assad family rule then descended into civil war. The armed forces have relied heavily on air power and artillery to hold
back the rebels.
Fighting has also spilled over the borders into Turkey, Lebanon, Jordan and the Israeli-occupied Golan Heights, raising
concern that the fighting could spread across the region, now home to 340,000 Syrian refugees.