Russia's 'blockade' of Sea of Azov port angers Ukraine Huge cranes that once used to unload ships' cargo sit idle on the docks of Ukraine's commercial port of Mariupol on the Sea of Azov. The small sea is located in a zone of heightened tensions between Russia and Ukraine: on the border of the Crimean peninsula annexed by Russia. As tensions escalate, Kiev and the West accuse Russia of deliberately blocking ships from accessing Ukraine's port.