There are reports of a large explosion on a bridge connecting occupied Crimea in Ukraine with mainland Russia.
Widely shared images show a train on the Kerch railway bridge on fire, with the road bridge next to it appearing to be constantly damaged.
Russian state media said a fuel tank was on fire without specifying a cause.
The bridge, opened by President Putin in 2018, is the only land connection to Crimea from Russia. Moscow had illegally annexed the region four years earlier.