The head of a Russia-dominated military alliance that is sometimes called Moscow's answer to NATO has said his organisation could send peacekeepers to territory in eastern Ukraine controlled by Russia-backed rebels if needed.
The situation in two self-proclaimed pro-Russian republics in Ukraine's Donbass region is on a knife-edge after rebel leaders declared a full mobilisation of their forces and asked civilians to evacuate to Russia following shelling which Ukraine and the separatist rebels blame on each other.
