Clashes between troops and rebels in Syria's western Latakia province killed 15 soldiers on Tuesday, the Syrian Observatory for Human Rights reported, bringing the day's death toll to at least 25.
"Fifteen soldiers were killed and dozens wounded, while three opposition fighters also died in continuing clashes in several villages of Al-Heffa region in Latakia," the Observatory's Rami Abdel Rahman told AFP.
The clashes took place in the villages of Bakas, Shirkak, Babna, Al-Jankil, and Al-Dafil in the Al-Heffa region, while troops stormed the town of Al-Heffa itself, according to Abdel Rahman.
State news agency SANA reported that "armed terrorist groups attacked citizens and security forces on Tuesday in Al-Heffa and tried to sabotage public and private institutions after the destruction of two ambulances used by medics in the city."
"The authorities have killed and wounded a number of terrorists in clashes," SANA reported, but did not specify how many. It added that two soldiers died.
Asked about the high number of troops killed in recent days, Abdel Rahman said: "This relates to the sharp increase in clashes across the country."
"Troops are vulnerable to heavy losses because they are not trained for street battles and are therefore exposed to attacks.
"What exacerbates those losses is that the army is fighting locals of those towns and villages, whether military defectors or civilians who took up arms against the regime, who know the area inside and out and enjoy public support."
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Opposition fighters are defending their towns by targeting approaching military vehicles with automatic weapons or grenades, which has taken a heavy toll on the army and security forces, he added.
The Observatory also reported clashes in the town of Kfar Zita in the central province of Hama, in villages in the northwestern province of Idlib, in the area of Lajat in the southern province of Daraa and near the town of Bianoon in Aleppo province in the north.
Six other people died in violence across the country Tuesday, including four civilians killed in a "huge military operation" before dawn in the Kfar Oweid district of Idlib province, according to the Britain-based watchdog.
In the northeastern city of Deir Ezzor, gunmen assassinated an army colonel in front of his home, the Observatory said, while a general was killed by a roadside bomb in the neighbourhood of Barzeh, the Observatory added.
SANA reported that "an armed terrorist group" targeted the car of General Anwar Sakka as he was "taking his daughter to her exams in the outskirts of Barzeh."
"The terrorist group planted a bomb under the car of the general and detonated it. The general was killed on the spot and his daughter and driver survived with injuries," the news agency said.
SANA reported that "terrorist groups" killed three army officers in all, including the general in Barzeh and two others in Deir Ezzor.
At least 38 people were killed in violence across the country on Monday, including at least 18 civilians, the Observatory said, adding that huge night-time protests were held in several provinces.