Moscow is set to bolster its Black Sea fleet with more submarines and warships, Russian Defence Minister Sergei Shoigu has said, as unrest in Ukraine rages on.

"This year, our sea bases will host new air defence and marine regiments. This year, the Black Sea Fleet will get new submarines and next-generation surface ships, and all of this requires our immediate attention," he told reporters.

The Russian minister insisted that Russia's recent annexation of Crimea has necessitated the latest measures. Russia intends to spend nearly $2.5bn (£1.47bn, €1.79bn) in bolstering its interests in Crimea by 2020.

Meanwhile, the crisis in eastern Ukraine deteriorated with Kiev's interim administration saying nearly 30 pro-Russian separatists have been killed in the latest skirmishes.

"We estimate that the terrorists lost more than 30 people," Kiev's Interior Minister Arsen Avakov said, adding that four Ukrainian troops had been killed earlier.

Another 20 Ukrainian security personnel were injured during the government operation in Slovyansk.

In Donetsk, about 120kms from Slovyansk, the main airport has been shut down and all flights cancelled.

The Ukrainian parliament is holding an emergency meeting to discuss the intensifying crisis in the eastern region. During the session, the security chiefs are expected to brief the policymakers about the latest situation.