Ukrainian troops have been placed on alert along the de facto border with Crimea and facing rebels in the east.

The heightened tensions follow Russian accusations that Ukraine is carrying out armed incursions into Crimea.

Ukraine's envoy to the UN asked Russia to provide evidence of the claims, and said some 40,000 Russian troops were massed on the Crimea-Ukraine border.

His Russian counterpart told the UN Security Council of Moscow's "concern and outrage" at the alleged incursions

http://www.bbc.com/news/world-europe-37049313