Turkish fighter jets have struck ISIL targets in the northern Syrian border town of Jarablus, according to Turkish news media.
Wednesday's operation is a part of a joint campaign by Turkish special forces and the US-led coalition to clear fighters belonging to ISIL, or the Islamic State of Iraq and the Levant group, from the Syria-Turkey border.
"The operation, which began at around 4am local time (01:00 GMT), is aimed at clearing the Turkish borders of terrorist groups, helping to enhance border security and supporting the territorial integrity of Syria," the state-run Anadolu Agency quoted Turkish officials as saying.
INTERACTIVE: Timeline of attacks in Turkey
Turkey's CNN Turk television said the operation involved artillery and rocket shelling as well as warplanes.
It also said Turkish forces were waiting for a possible ground operation at the border.
Security sources quoted by Turkish television said a small contingent of special forces travelled a few kilometres into Syria to secure the area before a possible operation.
Footage from CNN Turk broadcasting live from the Turkish border town of Karkamis showed white plumes of smoke coming from atop hills from Jarablus across the border.
Turkey had pledged on Monday to "completely cleanse" ISIL fighters from its border region after a suicide bomber suspected of links to the group killed 54 people at a Kurdish wedding in the southeastern city of Gaziantep.
Turkey is also concerned about the growing influence of Syrian Kurdish groups along its border, where they have captured large expanses of territory since the start of the Syrian war in 2011.
Turkey sees them as tied to the PKK, which has been waging an armed campaign mainly in the country's southeast.
READ MORE: Meet the female Kurdish fighters battling ISIL
The military operation against ISIL comes as Syrian rebels backed by Turkey also say they are in the final stages of preparing an assault from Turkish territory on Jarablus, aiming to pre-empt a potential attempt by Syrian Kurdish YPG forces to take it.
The YPG, a critical part of the US-backed campaign against ISIL, took near complete control of Hasaka city on Tuesday.
The group already controls chunks of northern Syria where Kurdish groups have established de facto autonomy since the start of the Syria war - a development that has alarmed Turkey.