Beirut - At least eight people were killed by Syrian regime shelling of the rebel-held Idlib province on Friday, according to a monitoring group -- the highest daily toll since a Russian-Turkish demilitarisation zone was set up around the region.

The Syrian Observatory for Human Rights said the deaths occurred in the town of Jarjanaz, which lies on the inner edge of the 15-20 km deep zone agreed in September.

The agreement, struck between Russia, Syrian President Bashar Al Assad’s most powerful ally, and Turkey, which backs the rebels, staved off a regime offensive to retake Idlib and adjacent opposition-held regions.

The UN says around 3 million people live in those areas and has said a battle to restore Al Assad’s control there could be the worst of the seven-year-old war.

Russia has said rebels are trying to wreck the Russian-Turkish initiative and Damascus has said Turkey seems unwilling to implement it. But Turkey says the deal is going to plan.

The Observatory, a British-based monitoring group, has reported regular exchanges of fire between regime and rebels since the September deal. At least 18 people have been killed by regime shelling since then.

Idlib is held by an array of rebels, the most powerful being Hayat Tahrir Al Sham, an amalgamation of Islamist groups dominated by the former Nusra Front, an Al Qaida affiliate until 2016.

On Thursday, HTS said it had raided regime positions in a village in eastern Idlib province in response to regime attacks. In a statement on its Telegram channel, it said it had killed 10 people, injured others and captured ammunition.