Turkey has begun deploying military vehicles to Syria’s northwestern province of Idlib, where Russia-backed Syrian regime forces have accelerated an attack in recent weeks, seizing dozens of towns and displacing thousands, pro-Kurdish Rudaw news agency reported.

Approximately 15 military trucks loaded with howitzers and tanks moved through the town of Kırıkhan in Turkey’s southernmost Hatay province toward border units under heightened security measures, the agency said on Saturday.

The report follows a warning by Turkish President Recep Tayyip Erdoğan on Friday that Turkey could launch its fourth military offensive in Syria if attacks on civilians in the northwestern province continue.

Syrian regime forces, supported by Russian aerial bombardment, on Tuesday entered the town of Maarat al-Numan, one of the first towns in Idlib to rise up against President Bashar Assad which had been in rebel hands since 2012.

The offensive in Idlib is raising tensions between Turkey and Russia, which back opposing sides in the conflict, with Ankara challenging Moscow over the assault that began last year despite a Turkey and Russia brokered 2018 de-escalation deal.

Under the agreement, Turkey maintains 12 observation posts in the besieged area, which it has vowed not to vacate.

Turkey, home to some 3.6 million refugees, is also concerned over a fresh wave of refugees at its border.

A total of 390,000 people have fled northwest Syria between Dec. 1 and Jan. 27, 80 percent of which are women and children, according to a United Nations report on Thursday.