In an interview with Russia's REN TV on Sunday, Lavrov accused Turkey of "creeping expansion" in northern Syria to prevent Kurdish fighters from strengthening their positions.

"According to our information, they are digging in a few hundred meters from the border inside Syria," said Lavrov, adding that his government had reports of Turkish tanks on Syrian soil.

"While demanding that Kurdish positions are not reinforced in Syria, Turkey has started to declare it has a sovereign right to create some safety zones on Syrian territory," he added.

Turkey has long tried to push its Western allies to create a safe-zone inside Syria to protect refugees and rebel groups. But for Ankara, a safe-zone would also provide a way to counter the advances of Syrian Kurdish forces, who much to the ire of Ankara are supported by both the United States and Russia.

Relations between Moscow and Ankara took a dive after Turkey downed a Russian warplane along the border in November. Russia has since upped the ante, going after Turkey where it is most vulnerable - by playing the Kurdish card.

Last month, Syrian Kurdish fighters took advantage of Russian airstrikes on the Turkish-backed opposition to make battlefield gains, prompting Turkey tofire artillery at Kurdish positions in Syria.

Meanwhile, Moscow has called for the Syrian Kurds to be included in peace talks in Geneva, something Turkey has tried to block.

Differences over the Syrian Kurds have also stressed relations between the United States and Turkey, with Washington viewing the Kurds as some of the best fighters against the "Islamic State."

Ankara views the Syrian Kurdish fighters as an extension of the Kurdistan Workers' Party (PKK), which has fought a three-decade-long war against the state for greater autonomy and rights for Turkey's Kurdish minority.

Turkey is concerned Syrian Kurdish autonomy and expansion in Syria could have a knock-on effect on its own restive Kurdish population.

Shamil Shams/cw (Reuters, AP)