KIEV (REUTERS) - Ukrainian border guards on Monday reported a build-up of armoured vehicles on the Russian side of a narrow sea channel dividing Russia and the Ukrainian region of Crimea.

A border guard spokesman also said Russian ships had been moving in and around the port city of Sevastopol, where the Russian Black Sea Fleet has a base, and that Russian forces had blocked mobile telephone services in some areas.

The build-up of Russian armour was near a ferry port on the Russian side of the Kerch Channel opposite the Ukrainian city of Kerch.