Ankara deployed artillery and anti-aircraft units to the Syria border following clashes between the Syrian army and rebels that left Turkish citizens injured, Turkish media reported on Saturday.

The deployment follows Syrian army shelling that wounded two Turkish citizens on Thursday near the border city of Sanliurfa. President Bashar Assad’s forces fired artillery rounds at rebels in an attempt to retake control of the Tel Abyad border crossing.

The rebels captured the border crossing from government forces on Wednesday. Since late July, opposition forces have seized at least three key border crossings with Turkey and others on Syria’s eastern border with Iraq.

Turkey’s mobilization was the most recent fortification of its southern border with Syria. Ankara has transferred numerous armored and artillery units and missile batteries to the border provinces of Hatay and Sanliurfa since the June 22 downing of a Turkish reconnaissance aircraft by the Syrian military.

In related news, the Free Syrian Army announced on Saturday that it has relocated its headquarters to Syria from Turkey.

Brig. Gen. Mustafa al-Sheikh, who heads the FSA’s Military Council, told The Associated Press that the move aims to unite all rebel groups. He said Saturday that the move was made the week before, without specifying its new location.

FSA commander Col. Riad al-Asaad issued a video titled “Free Syrian Army Communique Number 1 from Inside” that the command has moved to “liberated areas.”

The FSA has been the most prominent of the rebel groups trying to remove President Bashar Assad from power. But its commanders have come under criticism in the past for leading from Turkey, and its authority over numerous locally-based networks of fighters is limited.

AP contributed to this report.