Turkey's prime minister has accused Russia of the "ethnic cleansing" of Sunni Arabs and Turkmen in northern Syria, where Moscow has been carrying out airstrikes for two months.
"They want to expel, they want to ethnically cleanse this area," Prime Minister Ahmet Davutoglu told reporters.
He said Russia wants to protect its bases and the strongholds of the Syrian government.
"Their fight is not against Daesh," the prime minister said, using an acronym for the Islamic State extremist group.
Davutoglu also warned that the Russian bombardment would lead to up to 3 million Syrians fleeing their homeland, adding to the refugee burden in Turkey and Europe.
"If this bombardment continues I cannot tell you how many more millions may come to Turkey," he warned.
More than 4 million Syrians have fled their homeland since the civil war started in 2011, with more than 2.2 million reaching Turkish soil.
Hundreds of thousands have since left Turkey, often taking perilous boat journeys to Europe.
The European Union has stepped up its cooperation with Turkey, hoping Ankara will stem the outflow of migrants to the bloc, promising some 3.2 billion dollars in aid.
Tensions between Ankara and Moscow have escalated since November 24, when Turkey downed a Russian jet over the Turkish-Syrian border.
Russia began airstrikes in September to prop up the government of Syrian President Bashar al-Assad, whose troops have been at a disadvantage in their fight against rebel groups.
Most of Russia's airstrikes appear to be targeting these rebels, including hardline Islamist groups such as Ahrar al-Sham and al-Nusra Front.
But some of Moscow's attacks have hit Turkmen militias, who have ties to Turkey, in addition to having fought alongside other rebels.
Turkey is a staunch supporter of various Syrian rebel groups, mainly comprising Sunni Arabs, battling al-Assad.
Some of the government strongholds are located in the Latakia and Tartus coastal regions, where al-Assad's family originates. Russia has a key naval base in the area.
Russia has accused Turkey of enabling Islamic State to smuggle oil and fund itself, charges that Ankara denies.
Turkey for years had a porous border with Syria, which was often used by militants to cross in and out of the country. But there have been signs in recent months of the army stepping up security.
The United States, an important Turkish ally, has admitted that the border to areas in Syria controlled by Islamic State is still not sealed off.
Syria's main opposition and rebel groups are currently meeting in Saudi Arabia, hoping to come up with a unified position for negotiations with major powers over the future of the country.
The Riyadh conference follows Syria peace talks held by top diplomats from 20 countries in October in Vienna, where al-Assad's closest ally, Iran, participated for the first time.
A major sticking point in Vienna was al-Assad's fate