Russia has been building up its forces on the Ukrainian border steadily over the past few weeks and now has an estimated 10-12,000 troops in the area, a Nato military officer said.
Russia had withdrawn the majority of the 40,000 troops it had on the border earlier this year, and there were fewer than 1,000 by the middle of June. Speaking on the condition of anonymity, the officer told Reuters:
"Our current assessment is that between 10,000 and 12,000 troops are now in the area ... In the last week alone, we have seen several units moving into the border region."
More top news
Northern Ireland's abortion laws break the EU human rights convention, Belfast High Court has ruled.
Police reopen investigation into brutal murder of David Clarke, 14-years after he was "savagely beaten" to death in his own home.
Flooded in January, farming-driven Malawi ends 2015 facing its worst drought for more than 20 years. And now a slower tragedy is unfolding.