Multiple casualties reported after gunmen storm Moscow concert hall

Gunmen have stormed a concert hall on the outskirts of Moscow and opened fire with automatic weapons. Multiple casualties have been reported.

Russian media say up to four gunmen dressed in camouflage gear were involved.

The attack comes just days after the US embassy in Russia issued a security alert that extremists had imminent plans to target large gatherings in Moscow.

Warning, this report contains very distressing images.