Twelve Syrian soldiers were killed on Wednesday by an Al-Qaeda linked group in northwest Syria, according to a war monitoring organisation, the highest such death toll in the region this year.

The Britain-based Syrian Observatory for Human Rights said "12 members of the regime forces, including an officer, were killed following suicide attacks carried out by special forces from the Hayat Tahrir al-Sham group (HTS), targeting regime forces positions in the north of Latakia province" adjacent to Idlib, the last major rebel stronghold in the northwest.

The death toll is the "highest among the regime forces in the region since last September", according to the observatory.

Rami Abdel Rahman, head of the Observatory, told AFP that the attack was part of "an escalation by HTS since Monday, which included attacks on regime forces on several fronts".

The Idlib region is subject to a ceasefire brokered by Russia and Turkey after a regime offensive in March 2020. Despite being repeatedly violated, the ceasefire is still largely holding.

HTS controls swathes of Idlib province and parts of neighbouring Aleppo, Hama and Latakia.

More than five million people, most of them displaced, live in areas outside government control in the Idlib region.

HTS, considered a terrorist organisation by Damascus, the United States and the European Union, regularly clashes with Syrian and allied Russian forces.

It is the main rebel organisation active in northwest Syria, but there are other groups, some backed by Turkey.

Syria's war broke out after President Bashar al-Assad repressed anti-government protests in 2011, and has killed more than 500,000 people, displaced millions and battered the country's infrastructure and industry.