One Turkish soldier died on Saturday after shelling by Syrian President Bashar al-Assad's regime on the last rebel holdout of Idlib, the defence ministry said.

"One of our heroic comrades was injured as a result of tank fire by the regime on our elements who are in the Idlib region to ensure a ceasefire but fell martyr when he was being taken to a hospital," the ministry said on Twitter. The latest casualty brings the number of Turkish personnel killed in clashes in Idlib this month to 17.

The Turkish military retaliated and destroyed 21 regime targets following "the despicable attack", the ministry added. "The blood of our martrys will not be wasted."

The latest incident comes two days after two Turkish soldiers were killed in an air strike in the Idlib region blamed by Ankara on the regime in Damascus.

Turkey has 12 observation posts in Idlib as part of a Turkey-Russia deal, but Ankara's forces have come under attack this month from Syrian regime forces. The latest killings sparked a flurry of diplomatic activity this week, with President Recep Tayyip Erdogan urging his Russian counterpart Vladimir Putin, in a phone call Friday, to restrain the regime's offensive.

Russian air strikes in the northwestern province of Idlib are bolstering a months-long Syrian government onslaught that has forced nearly one million civilians to flee -- the biggest displacement of the nine-year conflict.

Regime supporter Moscow has accused rebel backer Ankara of failing to act against "terrorist groups in Idlib", which Turkey denies.