At least 33 Turkish soldiers have been killed in an air strike by Syrian government forces in north-west Syria, the BBC quotes a senior Turkish official as saying.
More were hurt in Idlib province, said Rahmi Dogan, the governor of Turkey’s Hatay province.
Turkey retaliated by attacking Syrian government targets.
Russia, Syria’s key military ally, said the Turkish troops had been operating alongside jihadist fighters when they were attacked by Syrian forces.
It denied its own air force had been involved in the fighting in the Behun area.