Russian troops have entered Ukraine, says NATO

NATO has noticed columns of Russian military equipment and combat troops entering Ukraine this week, a senior NATO commander said.

"Russian tanks, Russian artillery, Russian air defence systems and Russian combat troops" were sighted, BBC quoted US Gen Philip Breedlove as saying in Bulgaria.

Russia has always denied sending troops into eastern Ukraine to strengthen pro-Russian separatist rebels there. But the rebels have admitted being helped by Russian "volunteers".