Turkish President Recep Tayyip Erdogan has said that his country "cannot endure" Russian aircraft violating its airspace along the Syrian border, warning that "an attack on Turkey means an attack on NATO."
Erdogan addressed the incursions, which have occurred amid Russia's ongoing air campaign in Syria, during an October 6 press conference in Brussels.
"If Russia loses a friend like Turkey, with whom it has been cooperating on many issues, it will lose a lot, and it should know that," he said.
Erdogan accused Tehran and Moscow of working to maintain the "state terror" of Syrian President Bashar al-Assad.
Turkey has twice summoned Russia's ambassador to Ankara after Russian warplanes twice violated Turkish airspace over the weekend.
Moscow says a violation on October 3 lasted a few seconds and was due to bad weather. It says it is looking into claims of a second violation on October 4.
The Turkish military said on October 6 that eight Turkish F-16 jets carrying out reconnaissance flights over the Turkish-Syrian border were put on radar lock by an unidentified MIG-29 aircraft "for a total of four minutes and 30 seconds."
Radar lock-on enables missile systems to automatically follow a target.
In a separate incident on October 5, the same Turkish jets were also "harassed by missile systems deployed in Syria for a total of four minutes and 15 seconds," the military added.
NATO Secretary-General Jens Stoltenberg said earlier on October 6 that Russia's violations of Turkish airspace "does not look like an accident."
"Incidents, accidents, may create dangerous situations," he said.
Russia, which began its aerial campaign in Syria on September 30, says it is targeting the Islamic State (IS) group and other Islamists.
But NATO and allied states have expressed concern that Russia is concentrating its attacks on other groups opposed to President Assad.
Russia's latest air strikes in Syria included targeting IS-controlled sites around Palmyra.
The Britain-based Syrian Observatory for Human Rights said Russia has carried out at least 34 strikes in and around Palmyra in the last 24 hours.
Strikes were also reported near the city of Raqqa, the IS group's de facto capital.
The Observatory said at least 34 IS militants were killed in the strikes, which targeted 12 vehicles and two arms depots.
"All reports by foreign media that Russian planes allegedly struck the city of Palmyra are an absolute lie," Russian Defense Ministry spokesman Igor Konashenkov later said. "Our planes in Syria do not strike populated areas and especially ones with architectural monuments."
The Defense Ministry later said Russian aircraft flew 20 sorties on October 6, striking 12 IS targets around the eastern city of Deir Ezzor and in the provinces of Damascus, Idlib, and Latakia.
It said the jets hit "logistical infrastructure, command posts, training camps and bases."
Meanwhile, Deputy Defense Minister Anatoly Antonov said Moscow wants broad discussions on cooperation between Russia and the U.S.-led coalition fighting the IS group.
"Regrettably, the Americans would like to limit our cooperation to technical issues relating to interaction between our pilots while on relevant missions," Antonov said. "The Americans have handed us a document, on which we are working."
Konashenkov, a Defense Ministry spokesman, said Ankara suggested to Moscow that the two sides should consider creating a joint working group to coordinate actions related to Russia's air strikes in Syria.
Konashenkov said Turkey's Defence Ministry made the suggestion to a Russian military official attached to the Russian Embassy in Istanbul.
With reporting by AP and AFP