BEIRUT: Turkey defied international calls and shelled parts of northern Syria for a third day on Monday, insisting it would not allow Kurdish-led forces to seize key areas along the border.

The Turkish assault continued despite calls from its Western allies for restraint and drew fierce criticism on Monday from Russia, which said the “provocative” shelling was “creating a threat to peace and security in the Middle East and beyond."

The cross-border Turkish artillery fire, which began on Saturday, has added to an increasingly complex situation in Syria's northern Aleppo province just days before the ceasefire is due to begin.

Top diplomats from world powers agreed at talks in Munich last Friday on a “nationwide cessation of hostilities” within a week, in the latest bid to find an end to Syria's five-year conflict.

But advances in recent days by Kurdish and Syrian government forces in Aleppo province have raised deep concern in Ankara.

Following similar fire on Saturday and Sunday, Turkish shelling again hit several parts of Aleppo province on Monday.

Kurdish-led forces advance

Among the areas hit was a road west of the town of Tal Rifaat, where a coalition of Kurdish and Arab fighters known as the Syrian Democratic Forces (SDF) have launched an assault.

The town, only 20 kilometres from the Turkish border, is held by an alliance of mostly militant and terrorist forces and is one of their few remaining bastions in the area.

The shelling killed at least two children in the area on Monday, said the Syrian Observatory for Human Rights.The SDF was advancing despite the shelling, it said, and there was heavy fighting inside the western limits of Tal Rifaat.

The SDF has already seized the nearby Minnigh airbase from rebel forces, and severed the road between Tal Rifaat and the key rebel-held town of Azaz on the border with Turkey.

Turkey fears the Kurds will be able to create a contiguous Kurdish territory just across the border in northern Syria.

Turkey's Prime Minister Ahmet Davutoglu warned Monday that Ankara “will not let Azaz fall” to the SDF, adding “the necessary intervention will be made”.

He also warned the SDF to withdraw from the Minnigh airbase, saying it would be “rendered unusable” if they failed to do so.

The situation is a major headache for Washington, which has backed the Kurds in their battles against the militant Islamic State (IS) group despite the discomfort of fellow NATO member Turkey.

In recent days, Washington warned the Kurds not to “take advantage” of the situation in Aleppo to seize new territory.

Turkey is also a key member of the US-led coalition, and is allowing coalition planes to carry out sorties from its Incerlik base.

Ankara's shelling has prompted criticism from Damascus, which has urged the UN Security Council to take action.

Turkey on Monday also denied claims it had sent troops into northern Syria and rejected reports it was planning a ground intervention.

'Air raids' kill civilians

Russia, a key backer of President Bashar al-Assad which launched air strikes in Syria last year, said it would support the issue of the Turkish shelling being raised at the Security Council.

Moscow and Ankara have repeatedly clashed over Syria and on Monday Davutoglu issued a stark warning.

“If Russia continues behaving like a terrorist organisation and forcing civilians to flee, we will deliver an extremely decisive response,” Davutoglu said.

The Russian strikes have allowed government troops to press a major operation in Aleppo that has virtually encircled rebels in the east of Aleppo city, as well as pushing them from much of the region north of the city.

Moscow says its strikes target IS and other terrorists organisations.

On Monday, the Observatory said nine people including a child were killed when a suspected air strike hit a hospital supported by MSF near Maaret al-Numan in Idlib province.

MSF confirmed that a hospital it supports in the northwestern province had been destroyed in air strikes and said eight members of staff were missing.

“The destruction of the hospital leaves the local population of around 40,000 people without access to medical services in an active zone of conflict,” said MSF Syria operations chief Massimiliano Rebaudengo.

The Observatory also reported 10 civilians, including three children, were killed in another suspected air strike in Azaz and an area nearby.

The strikes in Azaz hit near a hospital, the monitor said.