The RS-26 is classified as an ICBM under a nuclear arms reduction treaty between the United States and Russia, but can be seen as an intermediate-range ballistic missile when used with heavier payloads at ranges below 5,500 km, the Centre for Strategic and International Studies said.
But Western missile experts have cast doubt on whether an ICBM was launched by Russia.
Andrey Baklitskiy, a weapons of mass destruction senior researcher at the United Nations, pointed out that Moscow did not inform Washington of the launch 24 hours in advance, as is custom.
“There’s a lot we don’t know,” said Mr Baklitskiy. “If true, this will be totally unprecedented and the first actual military use of an intercontinental ballistic missile. Not that it makes a lot of sense, given their price and precision.”
The RS-26 Rubezh weighs 50 tonnes and carries a warhead three times larger than the Iskander missiles.
The missile has been described as being in an “experimental” phase, given that it has barely been test fired. It can fly at five times the speed of sound, which makes it hard for the Patriot missile systems that guard Kyiv to shoot down.