KIEV - More than 10 Russian military helicopters flew from Russia into Ukrainian airspace over the Crimea region on Friday, the Ukrainian border guard service said on Friday.
It also said in a statement that Russian servicemen were blocking off a unit of Ukrainian border guards in the port city of Sevastopol, where part of the Russian Black Sea fleet is based.
Russia's Black Sea fleet had earlier on Friday denied any role in the seizure of a military airport near Sevastopol.
Andriy Paruby, secretary of the National security and Defence Council, the top security official in Ukraine's new power structure, stated to Interfax news agency on Friday that a declaration of a state of emergency in the southern region of Crimea is one of the options being studied to resolve the crisis unfolding there.
However, he also stated that the army would not be deployed and other options to localize the crisis would be considered.