'Fiercest' shellfire yet around Syria demilitarised zone

Rebels and 'radical' fighters have traded fire with government forces in northern Syria overnight, their "fiercest" exchanges since a buffer zone deal was announced for the area last month, an activist group has said.

A 15- to 20-kilometre wide "demilitarised zone" was announced by rebel-backer Turkey and government ally Moscow on September 17 to separate government troops from rebel fighters in their last major bastion in Idlib province and adjacent areas.

Shelling has continued intermittently, however, and escalated dramatically late on Wednesday, the Syrian Observatory for Human Rights said.

"It was the fiercest bombing yet since September 17," said Rami Abdurrahman, who heads the UK-based group.

"Syrian government rocket and artillery fire killed one girl in Kafr Hamra," an Aleppo province town inside the declared buffer zone.

Rebel shelling from inside the zone killed three civilians in government-held territory earlier this week, the AFP news agency reported.

Late on Wednesday, rocket fire by both 'radical' fighters and Turkish-backed rebels hit Aleppo, wounding 10 people, Abdurrahman said.

State news agency SANA gave the same casualty toll and said the army responded against the sources of the fire north and northwest of the city.

The National Liberation Front, the Turkish-backed rebel alliance which is the main armed group in that area, said it was responding to government violations of the truce deal with "light and medium weapons".

Under the deal agreed by Russia and Turkey, the rebels were supposed to have removed all heavy weapons from the buffer zone by 10 October.

Hayat Tahrir al-Sham (HTS), the alliance which is the dominant faction in Idlib, and other hardliners were supposed to leave the zone by 15 October.

But 10 days on there is still no sign of any pullout or of the planned monitoring patrols by the deal's co-sponsors, the Observatory said.

Syrian pro-government newspaper Al-Watan said HTS's failure to withdraw "provides the justification for the Syrian army and Russian air force to start a military operation to oust (HTS) from the area".

But both Russia and Turkey have said the truce deal remains on course despite the missed deadline, and their leaders are to be joined by their French and German counterparts for a four-way summit on Syria in Istanbul on Saturday.