Turkey sent artillery units to the border with Syria Saturday, where its army regularly clashes with Kurdish militia, the state-run Anadolu news agency reported.

A military convoy with at least five howitzers arrived overnight at the southern city of Kilis the scene of recent cross-border fire between the Turkish army and the Kurdish Peoples’ Protection Units (YPG).

The new units were there to reinforce rather than replace the artillery already in place, the agency reported, citing military sources.

Across the border from the province of Kilis lies an area of northwest Syria that is controlled by the YPG, which is Washington-backed but deemed a terror group by Ankara.

Turkish troops and YPG have exchanged fire in the region several times in recent months and Turkey has threatened to launch another cross-border offensive.

Turkey considers the YPG as the Syrian arm of the outlawed Kurdistan Workers Party (PKK), which has waged an over three decade insurgency against the Turkish state.

But the United States works closely with the group as the best ground force in Syria to defeat Islamic State (IS) militants. Turkey’s NATO allies do not regard the YPG as a terror organization.

Already in August 2016, Turkey launched a ground offensive into norther Syria to push back IS fighters and prevent the YPG forces linking up their different zones of control.