"Yesterday Russian soldiers took control of the town of Novoazovsk," Ukraine's National Security and Defense Council wrote on Twitter, adding that a number of surrounding villages had also been seized.
US Ambassador to Kiev Geoffrey Pyatt also said "an increasing number of Russian troops are intervening directly in fighting on Ukrainian territory."
"Russia has also sent its newest air defense systems including the SA-22 into eastern Ukraine and is now directly involved in the fighting," Pyatt wrote on Twitter.
After weeks of government offensives that have seen troops push deep into the last rebel bastions in the industrial east of Ukraine, the tide has turned dramatically in the four-month conflict.
Kiev called on NATO
...the North Atlantic Treaty Organization. A collection of multinational and multilingual and multicultural armed forces, all of differing capabilities, working toward a common goal by pulling in different directions...
for help after a rebel counter-offensive from the southeast border with Russia appeared to smash through an army blockade around the separatist stronghold of Donetsk and threaten the government-held port city of Mariupol.
Ukraine's Prime Minister Arseniy Yatsenyuk blasted Russian President Vladimir Putin
...Second and fourth President and sixth of the Russian Federation and the first to remain sober. Putin is credited with bringing political stability and re-establishing something like the rule of law, which occasionally results in somebody dropping dead from polonium poisoning. Under Putin, a new group of business magnates controlling significant swathes of Russia's economy has emerged, all of whom have close personal ties to Putin. The old bunch, without close personal ties to Putin, are in jail or in exile or dead...for having "deliberately unleashed a war in Europe" and called for an emergency UN Security Council meeting, a call echoed by Lithuania.