Pro-Russian soldiers are reported to have stormed a Ukrainian military base outside the Crimean city of Sevastopol, before withdrawing soon afterwards.

Two lorries from Russia's Black Sea Fleet were seen outside the gates, surrounded by armed men.

But no shots are believed to have been fired, and the assailants and lorries reportedly left after "negotiations".

Troops wearing Russian uniform without insignia have blockaded bases since taking control of Crimea last week.

Some military installations and other buildings in the peninsula have been taken over, but both sides have so far held their fire.