Syrian rebels have captured parts of a large army base in the country's north, just west of the city of Aleppo, activists say.
The Britain-based Syrian Observatory for Human Rights said the rebels entered the sprawling Sheikh Suleiman base on Sunday afternoon, after weeks of fighting.
The development indicates the rebels are strengthening their grip on northern areas near the Turkish border. Last month, they captured another large base near Aleppo.
Amateur videos released by activists showed fighters walking inside the base. The footage also shows rebels driving around in a captured tank and manning heavy anti-aircraft machine guns.
Among the groups that seized the base was the al-Nusra Front, which the US government is due to blacklist as a "terrorist organisatioon", documents released on Tuesday showed. The US says that al-Nusra is allied to al-Qaeda in Iraq.
Damascus air raids
Meanwhile, the Syrian military carried out an air strike on suburbs of Damascus, the capital, as rebels clashed on the ground with soldiers on Monday, the Observatory said.
In-depth coverage of escalating violence across Syria
"A fighter bomber carried out a raid on Daraya as rebels and soldiers fought on the ground, while artillery bombed Moadamiyet al-Sham," it said, referring to two towns south of Damascus.
The air force also overflew Eastern Ghouta, an area where rebels have set up rear bases amid its orchards, the Observatory said.
The military has for several days bombarded rebel strongholds in the suburbs from ground and air, raising fears of a looming ground assault by the army to try to establish a secure cordon around the capital.
Russia against 'recipes'
On the diplomatic front, Russia said plans for Syria's political future should not be forced on it from outside, underlining its hostility to foreign pressure for President Bashar al-Assad's exit and to Western backing for an opposition coalition.
In a statement Russia "stressed that fundamental decisions about reforming Syria's political system ... must be made by Syrians themselves, without outside interference or attempts to force prepared recipes for socio-political development" on them.
The US and its NATO allies have pressed for al-Assad's departure as part of efforts to end the bloodshed in Syria, but Russia and China have blocked action against the Syrian leader at the UN Security Council.
The Russian statement called for an immediate end to violence and "the start of a national dialogue during which representatives of the Syrian government and opposition should discuss and agree parameters of a transition period".
The statement also signalled opposition to Western backing of the opposition Syrian National Coalition, which the United States could soon recognise as the sole representative of the Syrian people.