Russia has said the number of Ukrainian military forces deployed in the southeast of the country should cause "deep concern" among members of the Organization for Security and Cooperation in Europe.
In a statement, the Russian Foreign Ministry said there were more than 11,000 Ukrainian troops, 160 tanks, 230 armoured vehicles and 150 artillery pieces deployed in the region as part of an operation to counter pro-Russian separatists.
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"People must be aware at all times that there are wild animals around them and they must make sure that their tents are properly closed."