Erdogan, Putin and Abbas attend a ceremony to open the Moscow Grand Mosque in Moscow.

Turkish President Recep Tayyip Erdogan on Tuesday warned Russia against losing Ankara’s friendship, after Russian warplanes twice violated its airspace near the Syrian border.

“If Russia loses a friend like Turkey with whom it has a lot of cooperation it is going to lose a lot of things. It needs to know this,” Erdogan said in Belgium at a press conference alongside Belgian Prime Minister Charles Michel broadcast on Turkish television.

In his toughest remarks yet against Russia in the current crisis, Erdogan accused Moscow and its ally Iran of working to maintain the “state terror” of Syrian President Bashar al-Assad.

His comments came after Russian warplanes twice violated Turkish airspace at the weekend during Moscow’s bombing campaign in Syria aimed at bolstering the Assad regime.

“It is of course not possible to remain patient about this,” said Erdogan, referring to the incursions into Turkish air space.

Erdogan, whose country is NATO’s only majority Muslim member, applauded the reaction of the alliance to Russia’s actions.

The NATO allies said Monday they “strongly protest” the violations by Russia and noted the “extreme danger of such irresponsible behavior.”

“An attack on Turkey is an attack on NATO, this needs to be known,” said Erdogan, referring to Article 5 of the NATO Treaty that states an attack on one ally is an attack on them all.

Russia accuses NATO of using Turkish incursion

Meanwhile, Russia’s NATO envoy said on Tuesday he thought the military alliance was using the accidental incursion of a Russian plane into Turkish airspace to distort the aims of Moscow’s air campaign in Syria, according to the TASS news agency.

“The impression is that the incident in Turkish airspace was used to plug NATO as an organisation into the information campaign waged by the West to distort the aims of the operations carried out by the Russian air force in Syria,” Alexander Grushko, Russia’s NATO envoy, was quoted as telling reporters in Brussels.

NATO on Tuesday rejected Moscow’s explanation that its warplanes violated the air space of alliance member Turkey at the weekend by mistake and said Russia was sending more ground troops to Syria.