Rebels launched a major assault Monday on two key military bases in northwestern Syria, with at least 14 people killed in the heaviest fighting the area has seen in months, activists said.
The offensive -- dubbed "The Earthquake" -- was aimed at seizing Wadi Deif and Hamidiyeh, which the insurgents have besieged for almost a year, said the Syrian Observatory for Human Rights.
Wadi Deif, a garrison housing a large quantity of weapons in Idlib province, is near Hamidiyeh, the last military stronghold in the region still held by Syrian President Bashar al-Assad's army.
Rocket and mortar fire from the rebels killed at least 10 soldiers and destroyed three tanks, said the Observatory, a Britain-based organisation that relies on activists across war-torn Syria for its information.
Four rebel fighters were killed in the clashes, which raged into the night.
The insurgents also captured an officer and three soldiers in a raid on Hamidiyeh, the Observatory said.
Forces loyal to Assad used helicopters to bombard the rebel positions around the two bases with barrels filled with explosives, it added.
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The insurgents have repeatedly tried to take control of the two bases over the past year, but to no avail.
Those involved in Monday's attack are from 25 brigades and small, mainly Islamist groups, including Liwa al-Umma, an Islamist brigade with Libyan fighters, said the Observatory.
The Syrian civil war has drawn in fighters from across the Arab world and beyond since it flared in response to a bloody government crackdown on democracy protests in 2011.
Elsewhere in the country, military air raids killed at least 10 people, including a citizen journalist, in the town of Hammuriyeh, east of Damascus, said the Observatory.
Air strikes also killed six people in Shaddadeh, an eastern town held by the jihadist Al-Nusra Front and the Al-Qaeda-affiliated Islamic State of Iraq and the Levant (ISIL), it added.
On Monday the army completely reopened the only supply route linking central Syria with the northern city of Aleppo after a year of fierce fighting between the two sides.
On August 26 the rebels had cut off the road following weeks of heavy clashes to prevent the Assad regime from sending reinforcements to Aleppo, the country's former commercial hub.