"We are working hard with Russia to stop these attacks. It is not possible to say a complete ceasefire has been secured," Cavusoglu told a news conference with his French counterpart Jean-Yves Le Drian in Ankara.

Moscow announced a ceasefire had been brokered with Turkey in the Idlib de-escalation zone as of midnight on June 12, after weeks of escalating rocket fire and air strikes by the Syrian regime and Russian forces.

Cavusoglu said there were "serious and sincere efforts" with Moscow to stop the violence, but said a full cessation had not been realised.

He also confirmed an earlier report that Syrian government forces had launched mortar attacks on a Turkish observation post in Idlib, injuring three soldiers.

"If the regime continues these attacks, we will do what is necessary," Cavusoglu said and called on Russia and Iran, who support the Syrian government, to "fulfil their responsibility".

Russia's defence ministry said the attack on the Turkish post was the work of "terrorists" and that it had responded with air strikes.

"On the night of June 13, terrorists bombed Turkey's military forces" in Idlib, it said in a statement.

"With the coordinates provided by the Turkish side, Russian planes carried out four strikes... destroying a large group of fighters."

But in a statement issued late Thursday, Turkey's defence ministry denied that assertion, saying incorrect "press reports" that it provided coordinates to the Russians "do not reflect the reality".

- 'Indiscriminate attacks'-

Idlib is supposed to be protected from a massive regime offensive by a buffer zone deal signed between Russia and rebel backer Turkey in September.

But it was never fully implemented, as jihadists refused to withdraw from the planned demilitarised zone.

The Syrian government and Russia have upped their bombardment of the region since late April, killing more than 360 civilians, according to the Syrian Observatory for Human Rights, a Britain-based war monitor.

Cavusoglu accused Syrian President Bashar al-Assad of seeking a military rather than a peaceful solution.

"We are seeing the increased attacks by the regime, especially targeting hospitals, schools and civilians recently in Idlib," he said. "This is a disaster in every manner."

Le Drian said the priority in Idlib must be to "restore calm and serenity to avoid a new humanitarian disaster."

"We call on the Syrian regime and its supporters to stop their indiscriminate attacks against civilians in Idlib," he said.

Syria's war has killed more than 370,000 people and displaced millions since it started in 2011 with the repression of anti-government protests.

Russia launched a military intervention in support of Assad in 2015, helping his forces to reclaim large parts of the country from opposition fighters and jihadists.