CRI听力:Russian Combat Troops Crossed Ukraine Border: NATO

NATO's top commander says Russian troops and tanks have been seen entering Ukrainian territory over the past few days.

U.S. General Philip Breedlove says their analysis is similar to that being seen by international observers.

"Across the last two days we have seen the same thing that OSCE is reporting. We have seen columns of Russian equipment, primarily Russian tanks, Russian artillery, Russian air defence systems and Russian combat troops entering into Ukraine."

Breedlove also says Russia has moved forces capable of delivering nuclear weapons to the Crimea region.

Russia's defence ministry has denied its troops are in Ukranian territory.

But at the same time, Russian Defence Minister Sergei Shoigu does say they want to strengthen Russia's armed forces in Crimea.

"The analysis of the possible development of the current events dictates the necessity to keep the military troops of the Southern military district in a state of readiness, to provide military security of the country and its allies in the south-west strategic direction."

The United Nations Security Council is convening an emergency session to discuss the reported Russian encroachment.

This comes amid reports of renewed fighting in the rebel-held cities of Donetsk and Luhansk.

A two-month-old ceasefire has appeared increasingly shaky over the past week.