Russian troops are entering Ukraine says NATO, as ceasefire collapses
"Russian tanks, Russian artillery, Russian air defence systems and Russian combat troops" have been seen, said US General Philip Breedlove, from a NATO air base near Naples.
The Reuters news agency quoted Breedlove as saying he was "concerned about the increased movement" of Russian military convoys "in the past several days".
Earlier this week, the Organization for Security and Cooperation in Europe (OSCE) warned of the "rising" risk of renewed open conflict.