A Ukrainian naval officer in Crimea has been killed by a Russian soldier, according to the Ukrainian Defence Ministry. The victim is reported to have been unarmed and the Russian is said to be under arrest and being detained in Sevastopol.

It comes as tension continue to rise between the two countries following a weekend of unrest involving pro-Russian protesters in several eastern cities. Russia annexed Crimea three weeks ago after a referendum in the peninsula in which the vast majority of residents voted to leave Ukraine.

Since then, Ukrainian soldiers have been ejected from their bases in the area by soldiers who are thought to be backed by Russia.

On Sunday, demonstrators in Donetsk and Luhansk demanded a referendum similar to that held in Crimea. Kiev has accused Moscow of orchestrating the violence.

Ukrainian Prime Minister Arseniy Yatsenyuk accused Russia of being behind a series of seizures of regional government buildings by protesters on Sunday.

He claimed that Moscow was trying to 'dismember' his country.

Mr. Yatsenyuk said "There is a plan to destabilise the situation, a plan for foreign forces to cross the border and seize the territory of the country, which we will not allow".

"This scenario is written by the Russian Federation and it's only purpose is to dismember Ukraine" he added.

He said Russian troops were within 30km (19 mile) of the Ukrainian border.

The dead soldier was apparently shot dead late on Sunday in the Crimean town of Novofyodorovka, about 30 miles west of Simferopol.