Turkish military crossed the border near the village of Cobanbey
Turkish tanks have crossed into northern Syria from Kilis Province to attack Islamic State.
The military crossed the border near the Turkish village of Cobanbey, which lies across from the Syrian village of al Rai, according to reports.
A Reuters cameraman in the area said he heard a repeated booming sound and saw plumes of smoke rising from the Syrian side of the border.
State media said troops are providing support to Syrian opposition fighters in al Rai, after ridding northern villages of extremists in its intervention.
The country began its cross-border offensive last month, with its tanks, artillery and warplanes backing Syrian rebels as they captured the town of Jarablus from Islamic State.
Last week, Turkey's president said his country will press ahead with its military operation in Syria, despite the US expressing "deep concern".
Recep Tayyip Erdogan vowed the offensive would continue until the Islamic State group and the Kurdish Syrian fighters no longer posed a threat to Turkey.
At the time, Mr Erdogan said: "Our operations will continue until terror organisations such as Daesh (Islamic State), the PKK and its Syrian arm, the YPG, cease to be threats for our citizens."
When the campaign was launched, Turkey's leaders said the aim was to target terrorists of Islamic State and the Kurdish-dominated militia.