On Thursday, three Turkish soldiers were killed in an air strike which the country's military blamed on the Syrian regime.
Turkey said it would retaliate after three of its soldiers were killed in what the military said was a suspected Syrian regime air strike.
Even though Turkey's prime minister Binali Yildirim did not explicitly blame the Syrian regime for the attack in the city of al-Bab, or confirm the Turkish army's suspicion, he was very clear that his country would respond to the aggression.
"It is clear that some people are not happy with this battle Turkey has been fighting against Daesh. This attack will surely have a retaliation," Yildirim told reporters in the capital Ankara.
Turkish forces are fighting the Daesh and PKK terror groups in northern Syria, part of Turkish military operation Euphrates Shield, in close proximity to other sides in the long running civil war, soon to enter its sixth year.
The Turkish army supports the efforts of the Free Syrian Army (FSA), which is also fighting Daesh. This would be the first time Syrian regime forces have killed Turkish troops during the current operation in a war that has claimed almost 300,000 lives.
The Syrian regime has made no official comment about Thursday's attack, but a pro-Bashar al-Assad site, Al Masdar News, quoted an unnamed Syrian official denying Damascus' involvement.
Turkish president Recep Tayyip Erdogan said in a speech in the capital Ankara last Wednesday that the FSA was close to taking the city of al Bab which is the last stronghold of Daesh in the northern Aleppo countryside.
The city is important to the Syrian regime, which has opposed Turkish involvement in its civil war. On Friday, Al Akhbar, a news site linked to Hezbollah, an Assad ally in the region, said that al Bab represents a "red line" which Ankara should not cross.
"The timing of the air strike targeting Turkish soldiers came to set Syria's redlines in the strategic region; storming Al Bab is forbidden," and that the strike "leaves Ankara no room for miscalculation or misunderstanding the message that the entry into Al Bab is forbidden," the article said, according to a report in Now Lebanon.
Syrian regime forces threatened Turkey last month, saying it would shoot down Turkish warplanes if they made any advance toward their positions in the north and east of Aleppo, considering the move as a "flagrant breach of Syria's sovereignty."
The advance by the largely Turkmen and Arab rebels towards Al Bab, the last urban stronghold of Daesh in the northern Aleppo countryside, potentially pits them against YPG fighters and Syrian government forces.
Turkey is backing the Syrian rebels with troops, tanks and artillery, as well as reconnaissance flights along the border, according to the Turkish military. Russian forces, backing their ally in Damascus, are also in the region, and Washington has accused them of targeting civilians on behalf of the Assad regime instead of Daesh fighters.