A key part of the road and rail bridge Russia is building across the Black Sea to Crimea has been towed out.

The motorway arch will be installed between pillars in the Kerch Strait, where a railway arch has already been erected, with ships able to pass under them eventually.

The 19-km (12-mile) bridge is due to open to cars in December 2018 and trains should be able to use it from 2019.

The bridge is a flagship political project for Russia as it seeks to cement its hold on Crimea, annexed from Ukraine in 2014 after an unrecognised referendum on unification with Russia.