Russia appears to have suffered a "catastrophic failure" in a test of its Sarmat missile, a key weapon in the modernisation of its nuclear arsenal, according to arms experts who have analysed satellite images of the launch site.

High-resolution satellite images of the launch pad at Russia's Plesetsk test site, where the RS-28 Sarmat ballistic missile exploded shows extensive damage.

Satellite images from Maxar dated September 21 show signs of a potential failure during a test of Russia's RS-28 Sarmat missile at Plesetsk Cosmodrome. A large crater and surrounding damage were observed,