Turkish tanks and other armored vehicles entered the Syrian province of Aleppo and shelled positions of Daesh militants, Hurriyet Daily news reported.
Turkish forces crossed the border from the Turkish province of Kilis, near the town of Cobanbey, some 25 kilometers from the place where the operation began.
In order to enter the Syrian territory, Turkish troops dismantled part of a wall which is currently being built on the border, DHA news agency reported citing military sources.
The Euphrates Shield operation started on August 24 in the northern Syrian city of Jarablus and was backed by a US-led international coalition. At the time, nearly 40 Turkish tanks backed by some 1,000 Syrian rebel forces entered Syria.
In response, Damascus accused Ankara of violating its national sovereignty.
According to the Turkish government, the operation is aimed against Daesh militants and Kurdish forces and will last as long as needed.
On Monday, the Turkish Foreign Ministry issued an ultimatum to Kurds and demanded from them to withdraw to the east from the Euphrates. The United States, in turn, criticized Turkey for attacking Kurds and called for strikes against Daesh.
The Russian Foreign Ministry called for Turkey not to attack Syrian opposition forces and Kurds. Moscow also stressed that all military operations in Syria should be coordinated with the Syrian government.