Bildt: Kremlin escalating conflict with Ukraine is dangerous

Reports of a build-up of Russian troops on its shared border with Ukraine is "significant" and could lead to open conflict, Carl Bildt, co-chair of the European Council on Foreign Relations has said.

He told BBC World News: "It's clearly a deliberate decision by the Kremlin to escalate the conflict. Where this will lead us - we don't know. But it's dangerous."

Russia has insisted the troop movements poses no threat to Ukraine and has warned Nato against sending any assistance to the country.