ANKARA (Reuters) - Turkey will use force against rebel groups violating a ceasefire in Syria’s northwest Idlib region, Turkish Defence Minister Hulusi Akar said on Thursday, in an apparent response to Russian criticism.

Turkey has allied with some rebels in Idlib opposed to Syrian President Bashar al-Assad, and has boosted its troops, arms and equipment in the region after 13 of its soldiers were killed by Syrian government forces in just over a week.

Turkish President Tayyip Erdogan has said his NATO-member military would strike Russia-backed Syrian forces if another Turkish soldier was hurt, and he blamed Moscow for targeting civilians.

Russia, which supports Assad, in turn accused Turkey of flouting agreements it made with Moscow and of aggravating the situation in Idlib. The Kremlin said Ankara had failed to neutralise militants there, as per a 2018 agreement to establish a de-escalation zone.

Apparently responding to the Russian criticism, Akar said Turkey was sending reinforcements to Idlib to ensure a ceasefire is maintained and to “control” the area, according to a ministry statement.

“Force will be used against those violating the ceasefire, including radicals, and every measure will be taken,” Akar said, referring to a Jan. 12 ceasefire Ankara says has been violated by Assad’s forces.

The flare-up of fighting has given rise to some of the most serious confrontations between Ankara and Damascus in the nine-year-old war that, since early December in Idlib alone, has displaced hundreds of thousands.

Aid workers said families fleeing air strikes and advancing troops in Idlib were sleeping in streets and olive groves, and burning toxic bundles of rubbish to stay warm in the biting winter weather.

Since last week, Ankara has deployed more than 1,000 troops to its military posts in Idlib.

On Wednesday, Erdogan said Ankara had given a message to the rebels it supports in the conflict to refrain from acting in an undisciplined way and give Syrian forces an excuse to strike.

The rebels are a mix of nationalist factions and Islamist militants who were rivals but are now closing ranks.

A Turkish official told Reuters: “Talks are being held with Russia to make sure tensions don’t flare more.” Yet he added rebels backed by Turkish artillery had in recent days retaken territory previously lost in Idlib.

Turkey has repeatedly urged Russia to stop the Syrian attacks in Idlib, warning that it will use military power to push back the Syrian forces unless they withdraw by the end of the month.

Later on Thursday, Russia called on Turkey to refrain from provocative statements about Idlib. It said it was “perplexed” by the comments of Erdogan’s nationalist partner party leader, who held Moscow responsible for attacks on Turkish troops and said Ankara should plan to “enter Damascus”.

“We believe that in the context of the tense situation in the north-west of Syria, it is worth exercising restraint and in particular refraining from provocative comments that do not contribute to a constructive dialogue between our countries,” the Russian foreign ministry said.

Ankara and Moscow back opposing sides, but have collaborated on a political solution to the war.