Russia has accused Turkish President Recep Tayyip Erdogan of being directly involved in the purchase of oil from the Islamic State as relations between the two former allies continues to deteriorate.
Russia has begun air strikes against rebel positions within Syria, with the first target near the western city of Homs, US defence officials say.
Vladimir Putin has said that a war between Russia and Ukraine is “unlikely”, despite the rising tensions between the two countries over the crisis in eastern Ukraine.
Russia poses a “real and present danger” to the stability of Latvia, Lithuania and Estonia, the UK defence secretary has warned.
The US is examining the option of supplying “lethal defensive weapons” to Ukraine if a peace deal is not reached to end the crisis in the east of the country, Barack Obama has said.