What is the ICBM Ukraine says Russia fired?

A Russian intercontinental ballistic missile (ICBM) that Ukraine says was fired at the city of Dnipro was an RS-26 Rubezh, Ukraine's Ukrainska Pravda media outlet reported, citing anonymous sources.

According to defence sources, however, there are doubts as to whether the weapon used was the RS-26 Rubezh, and said that an accurate assessment based on the available imagery would be difficult.

Here are some facts about ballistic missiles, ICBMs and the RS-26:

- A ballistic missile is a rocket-propelled, self-guided weapon that falls towards its target by force of gravity.

- An ICBM refers to a ballistic missile with a range of more than 5,500km.

- US think-tank the Center for Strategic and International Studies (CSIS) said that although the R-26 is classified as an ICBM under the New START nuclear arms reduction treaty between the United States and Russia, it can also fall into the category of an intermediate-range ballistic missile when used with heavier payloads at ranges below 5,500km.

Rapid Flight

- Ballistic missiles, including ICBMs, can be fired in a depressed mode, meaning that they do not enter space and their trajectory stays within the atmosphere. That would use up more fuel and reduces their range.

- ICBMs fly at speeds of several kilometres per second. An ICBM would take around 40 minutes to reach a target in the United States coming from Russia, according to a military source. The more than 700km journey to Dnipro from the Russian region of Astrakhan, from where Ukraine's air force said the weapon was fired, would take less than 10 minutes.

First successful test in 2012

- ICBMs are designed to carry nuclear warheads, although technically they can carry any payload of equal or lesser mass, with modifications. There was no suggestion that a nuclear weapon was fired by Russia.

- According to the US-based Arms Control Association, the RS-26 has a range of up to 5,800 km.

- The CSIS said the RS-26 was first successfully tested in 2012 and is estimated to be 12 metres long and weigh 36 tons and can carry an 800kg nuclear warhead.

It never formally entered service, according to experts.