Russia has started a build-up of armoured vehicles on the Russian side of a narrow stretch of water between Russia and the Ukrainian region of Crimea, Ukrainian border guards said on Monday.
A border guard spokesman also said Russian ships had been moving in and around the Crimean port city of Sevastopol, where the Russian Black Sea Fleet has a base, and that Russian forces had blocked mobile telephone services in some parts of Crimea.
He said the build-up of Russian armour was near a ferry port on the Russian side of what is known as the Kerch Strait, which separates the eastern edge of the Crimea peninsula and the western edge of the Taman Peninsula.
"There are armoured vehicles on the other side of the strait. We can't predict whether or not they will put any vehicles on the ferry," the spokesman said by telephone, Reuters reports.
To recall, Russia's upper house of parliament has authorised President Vladimir Putin to deploy troops in Ukraine to defend Russian speakers in Ukraine who are said by Moscow to be under threat.
Meanwhile, Ukraine has ordered a military mobilisation as well as putting its forces on combat alert.