Pro-Russian groups are holding protests in Ukraine's eastern city of Donetsk later. 

Militants occupied the city's regional government offices for three days this week, hoisting a Russian flag before being thrown out by police.

Rival demonstrations have brought thousands of people into the streets, some of those protests have developed into street battles.

The head of the Ukrainian border guards thinks more than 30-thousand members of the Russian military are now in the disputed Crimea peninsula.

That figure includes troops that have arrived over the last week and those in Russia's Black Sea Fleet, which has a base in Crimea.

Rear Admiral John Kirby is the Pentagon's Press Secretary: