Ukrainian officials have accused Russia of using an intercontinental ballistic missile (ICBM) for the first time in the warwhich, if confirmed, would be a deliberate and major escalation of the conflict and a signal to Kiev’s allies.

But Western officials and defense experts questioned whether Russia used an ICBM, which are designed to launch long-range nuclear strikes.

The Ukrainian Air Force said Russia had fired an ICBM at the city Dnipro in central Ukraine on Thursday, without specifying which type. It claimed the missile was launched more than 600 miles away from Russia’s Astrakhan region, which borders the Caspian Sea.

Ukrainian President Volodymyr Zelensky said the missile used “matches the speed and altitude” of an ICBM, and a specialist investigation is underway. Russia declined to comment on the report.

Images shared online of the dawn attack appeared to show several bright flashes of light traveling vertically toward the ground.

Open Source Intelligence Detectives suggested that the model rockets could be from “re-entry vehicles”which are warheads that separate from the missile. Longer-range ballistic missiles such as ICBMs have multiple independently targetable reentry vehicles (MIRVs) that allow operators to increase the destructive power of each missile.

Ukrainian media, citing unnamed officials, claimed that an RS-26 Rubezh missile was used in the attack targeting businesses and critical infrastructure, although this has not been confirmed by the Russian or Ukrainian governments.

The Rubezh missile is designed to carry nuclear warheads and is classified as an ICBM under the US-Russia New Start treaty, which limits the use of US and Russian nuclear warheads.

right Center for Strategic and International StudiesThe Rubezh is estimated to be 12 meters long, can carry an 800 kg nuclear warhead, and has a range of 2,000 km to 5,800 km (about 1,200 miles to 3,600 miles).

It can also fall into the category of an Intermediate-Range Ballistic Missile (IRBM) when used at ranges below 5,500 km (about 3,400 miles).

Timothy Wright, a research associate at the International Institute for Strategic Studies (IISS), said the alleged images of the attack appeared to show the characteristics of an ICBM.

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