Ukraine crisis: Tank traps placed on Russian border
President Vladimir Putin and the leaders of Crimea have signed a bill to absorb the peninsula into Russia.
In a televised address, Vladimir Putin said Crimea "had always been part of Russia", and denied he was interested in annexing more territory.
Steve Rosenberg reports from Ukraine's eastern border, where "tank traps" have been placed, and trenches dug in order to repel any Russian attack.
18 Mar 2014