Citing a military source, state television said Syria's "armed forces, in coordination with the popular defence (militia), seized control of the town of Rabia."
The town had been held by the opposition since 2012 and was controlled by a range of rebel groups including some made up of Syrian Turkmen, as well as Al-Qaeda affiliate Al-Nusra Front.
Syrian state news agency SANA said government forces were "combing the area to dismantle any explosive devices or mines planted by the terrorists, many of whom were killed."
According to the Syrian Observatory for Human Rights, Rabia fell on Sunday after a steady regime advance that left the town surrounded.
"In the past 48 hours, regime forces surrounded the town from three sides -- the south, west, and north -- by capturing 20 villages," Observatory head Rami Abdel Rahman told AFP.
Abdel Rahman said senior Russian military officials were overseeing the battle for Rabia, and that Russian air strikes "played an essential role" in the fight.
With the capture of Rabia, government troops are closing in on rebel supply routes through the Turkish border to the north, he added.
Rabia's fall comes after government troops seized the strategic town of Salma on January 12, following months of operations to capture it from rebels who had held it since 2012.
- Blocking rebel attacks -
Syria's government has been fighting to clear rebels out of their posts in the northern parts of Latakia province, particularly the regions of Jabal Turkman and Jabal Akrad.
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From those areas, armed opposition factions have carried out rocket and bomb attacks on the provincial capital along the coast.
Backed by Russian air power, pro-regime forces are chipping away at that territory in a bid to secure the Assad clan's heartland.
Syria analyst Fabrice Balanche said Rabia was the biggest population centre in the forested Jabal Turkman region.
"It is at the crossroads of supply routes in this region" leading northwest towards the Turkish border and further east to other rebel strongholds, Balanche told AFP.
"By controlling this road, the Syrian army can block rebel movements towards the south, towards Latakia, and the rebels will have a hard time getting close and firing missiles at the (coastal) airport," he added.
Since September 30, Russia's air force has operated out of the Hmeimim airport in Latakia province.
Moscow has been sharply criticised by rights groups for indiscriminate air strikes that have caused civilian casualties.
In a new toll it gave on Sunday, the Observatory said suspected Russian air strikes on a jihadist-held village in eastern Syria killed 63 civilians.
Nine children and two women were among those killed in the raids Saturday on Khasham, a village controlled by the Islamic State jihadist group in the Deir Ezzor province.
The Britain-based monitor uses a broad network of medics, activists, and fighters to compile death tolls and identifies aircraft by flight patterns and munitions used.
More than 260,000 people have been killed since Syria's war erupted in 2011.