Russia is accusing Turkey of supplying the Islamic State extremist group with components for improvised explosive devices.

Russia's U.N. Ambassador Vitaly Churkin said in a letter to Secretary-General Ban Ki-moon circulated Wednesday that the devices "are being widely used to commit terrorist acts."

Churkin accused five Turkish companies of delivering aluminum powder, ammonium nitrate, hydrogen peroxide and other material produced by Turkish and foreign companies to IS.

Turkey's Foreign Ministry spokesman in Ankara responded saying: "The said letter is the most recent example of Russia's propaganda campaign against Turkey, and as such it cannot be taken seriously."

Russia, a close Syria ally, and Turkey, a major opposition backer, have been at odds during the conflict. Tensions escalated following Turkey's downing of a Russian warplane near the Syrian border last November.