The Turkish President Recep Tayyip Erdogan appeared to say that Ankara is planning to deploy ground forces to attack Kurdish forces based across the border in Syria.

Turkey blames the groups for the November 13 bombing in central Istanbul, that killed six people. Russia has warned against any potential operation.

“We have been bearing down on terrorists for a few days with our planes, cannons and guns,” Erdogan said in a speech on Tuesday.

“God willing, we will root out all of them as soon as possible, together with our tanks, our soldiers.” he added

Erdogan has made similar threats in the past six months, but cross-border air raids on Sunday have heightened the possibility that a bigger military operation may occur.

The Kremlin has said Russia respects Turkey’s “legitimate” security concerns over Syria but claimed all parties there should avoid steps that could worsen the situation.

Kremlin spokesman Dmitry Peskov told reporters on Tuesday that while there were disagreements between Russia and Turkey in their approach to Syria, Moscow understood Turkey’s security concerns.

Ankara blamed the outlawed Kurdistan Workers’ Party (PKK) and affiliated Syrian Kurdish groups for the Istanbul attack, which also saw more than 80 people wounded.