By Tom Balmforth

(Reuters) – Ukrainian investigators are studying the debris of a new Russian intermediate-range ballistic missile that was fired at the city of Dnipro on Thursday, the first time such a powerful weapon has been used in the war.

Reuters was among a small group of reporters given access to the wreckage of the missile on Sunday. Reporters were asked not disclose the exact location of the site for security reasons.

The scorched and crumbled pieces of debris were laid out in a hanger at a facility which conducts weapons forensics. Ukrainian experts study such debris to gain insight into Russian military supply chains, production and how to develop counter-measures.

Russia has dubbed the missile the Oreshnik (Hazel Tree) and said it is impossible to intercept it with air defences. Ukraine has said the weapon reached a top speed of more than 13,000 kph (8,000 mph) on its way towards Dnipro on Thursday.

Intermediate-range ballistic missiles have a range of up to 5,500 kilometres.

Two state experts provided cautious assessments, saying only that the weapon was ballistic, flew on a ballistic trajectory and that the strike resulted in civilian damage. They declined to take questions or give their surnames.

“These are preliminary conclusions and to say something more concrete requires time and careful study of the remains of the missile,” said Ivan, one of the experts.

“This is the first time that such remnants of such a missile have been discovered on the territory of Ukraine,” said Oleh, an investigator for the Security Service of Ukraine.

Ukrainian President Volodymyr Zelenskiy has called the use of the weapon a severe escalation and urged his allies to respond. Ukraine originally said the weapon appeared to be an intercontinental ballistic missile.

The Kremlin later said it fired a new intermediate-range missile at a Ukrainian military target in Dnipro in response to Kyiv striking Russia with U.S. and British made missiles for the first time after the U.S. granted its approval.

The U.S. military has said the missile’s design is based on the longer-range RS-26 Rubezh intercontinental ballistic missile (ICBM). The new missile was experimental and Russia likely possessed only a handful of them, they have said.

Russian President Vladimir Putin said on Friday Moscow would keep testing the missile in combat and had a stock ready to use.

Much remains unclear for now, including the extent of the damage caused by the missile. Ukraine seldom discloses damage to military targets, fearing such information would help Moscow.