At least 30 Syrian soldiers have been killed by foreign-backed militants fighting against the Arab country’s government following the fall of a key town in the northwestern province of Idlib, a monitoring group says.

Al-Qaeda-linked al-Nusra Front and allied militant groups executed 12 Syrian troops in Ariha hours after the militants captured the town, the so-called Syrian Observatory for Human Rights said on Friday.

A fighter from Lebanon's resistance movement Hezbollah, battling along with the Syrian forces, was also killed by the terrorists, the UK-based observatory added.

According to the observatory, 18 other Syrian troops were also shot dead as they were trying to withdraw from the town.

The extremist groups marched into Ariha, located around 20 kilometers (12 miles) southwest of the provincial capital, Idlib, on Thursday and wrested control over it following fierce exchanges of fire with Syrian government forces.

Ariha was the last remaining government-held town in Idlib. On March 28, the provincial capital fell into the hands of the militants.

Syria has been grappling with deadly foreign-backed militancy fueled by Takfiri groups since March 2011. More than 222,000 people have so far been killed in the crisis, according to the UK-based monitoring group.

Over 3.8 million Syrians have also fled the violence to other countries, and more than 7.2 million others have become internally displaced, according to the United Nations.

MSM/AS/MHB