Russia has evidence that Turkish troops are on Syrian territory, Russian Foreign Minister Sergei Lavrov said in an interview broadcast on Sunday, accusing Turkey of a "creeping expansion" on its border with Syria.
The comments by Lavrov are the latest confrontation between Moscow and Ankara, after Turkish jets shot down a Russian warplane near the Turkish-Syrian border in November.
"Turkey has started to declare it has a sovereign right to create some safety zones on Syrian territory," Lavrov told Russian television channel Ren-TV. "According to our data, they have already 'dug themselves in' several hundred metres from the border in Syria. ... It's a sort of creeping expansion."
Lavrov also said that Russia would insist the United Nations invites Kurds to peace talks on the Syrian conflict despite Turkey's opposition.
Russia and Turkey are on opposing sides of the five-year-old conflict in Syria. Relations between the two countries nose-dived after the downing of the Russian plane, which President Vladimir Putin called a "stab in the back".
Turkish President Tayyip Erdogan has not apologised over the incident, saying the Russian jet crossed into Turkish airspace and ignored repeated warnings. Russia denies the warplane violated Turkey's airspace.
Lavrov added to Ren-TV that Russia was willing to co-ordinate its actions in Syria with the United States so that the city of Raqqa could be taken back.
"At some stage the Americans suggested carrying out a 'division of labour': Russia's air force should concentrate on freeing Palmyra and the US coalition with Russian support should concentrate on freeing Raqqa."