Jihadists killed at least 11 Syrian soldiers in the war-torn country's northwest Saturday when they detonated explosives placed in tunnels dug underneath army positions before attacking them, a monitor said.

The attack involving jihadists from the Ansar al-Tawhid group and the Turkestan Islamic Party (TIP) took place in the south of Idlib province, said the Syrian Observatory for Human Rights.

The jihadists "detonated tunnels they had dug beneath army positions and simultaneously launched an assault from other tunnels", said Rami Abdel Rahman, who heads the Britain-based Observatory.

The attack, which also wounded 20 soldiers, comes a day after Russia carried out air strikes on the Jisr al-Shughur region near Idlib, where TIP jihadists are present, the Observatory said.

Both groups involved in the attack are affiliated with the jihadist Hayat Tahrir al-Sham (HTS) group, which controls swathes of Idlib province as well as parts of the adjacent provinces of Aleppo, Hama and Latakia.

Seven HTS fighters were killed Friday in bombardments by government forces and at least 13 others in Russian air strikes Monday in northern Syria, said the Observatory, which relies on a network of sources on the ground in Syria for its reports.

Two civilians were also reported to have been killed by Russian strikes near Idlib.

The war monitor said "two jihadists took their own lives" in Saturday's attack and that the death toll was expected to rise as the "intense clashes are still ongoing".

Syria's civil war broke out in 2011 when the government's repression of peaceful protests escalated into a conflict that drew in foreign powers and jihadists from abroad.

Russia intervened in the conflict in 2015 on the side of President Bashar al-Assad, launching air strikes to support his government's struggling forces.

The TIP is largely made up of jihadists from China's Uighur Muslim minority who came to Syria after 2011 to assist groups like HTS, which is led by Al-Qaeda's former affiliate in Syria.

The rebel-held region of Idlib is home to about three million people, around half of them displaced from elsewhere in Syria.

A ceasefire deal brokered by Russia and rebel-backer Turkey has largely held in Syria's northwest since 2020, despite periodic clashes.

The Syrian war has killed more than 500,000 people and forced around half of the country's pre-war population to flee their homes.