Story highlights Putin says Turkey downed plane to secure oil routes with ISIS

Erdogan says he'll resign if Putin can prove that claim

Turkey, Russia are at odds on how to end the Syrian civil war

(CNN) Tensions between Russia and Turkey, already playing different roles in Syria's bloody civil war, escalated with the downing of a Russian warplane on November 24.

It's the most recent clash in a series of disputes between the two countries.

Russian President Vladimir Putin on Monday accused Turkey of shooting down the plane to protect secret oil trade with the terrorist group ISIS. He said the plane was actually going to attack ISIS targets in Syria.

Turkish President Recep Tayyip Erdogan said the plane violated Turkish airspace. He said he'll resign if Moscow can prove its claim.

"As soon as such a claim is proved, the nobility of our nation requires (me) to do this," Erdogan told reporters at the climate change summit in Paris on Monday.