Russia launched an intercontinental ballistic missile during an attack on Ukraine on Thursday, Kyiv's air force said, in the first known use in the war of a powerful weapon designed to deliver nuclear strikes thousands of kilometers away.

The launch was the latest sign of rapidly mounting tensions in the 33-month-old war after Ukraine fired U.S. and British missiles at targets inside Russia this week despite warnings by Moscow that it would see such action as a major escalation.

Security experts said that, if confirmed, it would be the first military use of an ICBM – strategic weapons designed to deliver nuclear warheads and are an important part of Russia's nuclear deterrent.

The Ukrainians did not specify what kind of warhead the missile had or what type of missile it was. There was no suggestion it was nuclear-armed.

Russia did not immediately comment on the Ukrainian air force statement. Asked by reporters about the air force statement, Kremlin spokesman Dmitry Peskov told reporters to contact the Russian military for comment.

Ukrainska Pravda, a Kyiv-based media outlet, cited anonymous sources saying the missile was an RS-26 Rubezh, a solid-fueled intercontinental ballistic missile with a range of 5,800 km, according to the Arms Control Association.

The RS-26 was first successfully tested in 2012, and is estimated to be 12 meters (40 ft) long, weighing 36 tons, according to the Centre for Strategic and International Studies (CSIS). It said the RS-26 can carry an 800-kg (1,765-pound) nuclear warhead.

The Russian missile attack targeted enterprises and critical infrastructure in the central-eastern city of Dnipro, the air force said.

The air force did not say what the ICBM had targeted or whether it had caused any damage, but the regional governor, Serhiy Lysak, said the missile attack caused damage to an industrial enterprise and set off fires in Dnipro. Two people were hurt.

Russia also fired a Kinzhal hypersonic missile and seven Kh-101 cruise missiles, six of which were shot down, the Ukrainian air force said.

"In particular, an intercontinental ballistic missile was launched from the Astrakhan region of the Russian Federation," it said.

Astrakhan is more than 700 km (435 miles) from the Ukrainian city of Dnipro.

'Totally Unprecedented'

Defense Express, a Ukrainian defense consultancy, asked whether the United States, Kyiv's main international ally, had been informed about the missile launch ahead of time.

"It is also a question of whether the United States was warned about the launch and its direction, as the announcement of such launches is a prerequisite for preventing the triggering of a missile warning system and the launch of missiles in response," Defence Express wrote.

The NATO military alliance did not immediately respond to a request for comment.

"If true this will be totally unprecedented and the first actual military use of ICBM. Not that it makes a lot of sense given their price and precision," Andrey Baklitskiy of the U.N. Institute for Disarmament Research posted on X.

German security expert Ulrich Kuehn posted: "It looks as if Russia has today used an intercontinental ballistic missile in a war for the first time in history, against the civilian target Dnipro."

Russian war correspondents on Telegram and an official speaking on condition of anonymity said Kyiv fired British Storm Shadow cruise missiles into Russia's Kursk region bordering Ukraine on Wednesday.

A spokesperson for Ukraine's General Staff said he had no information and the extent of any damage caused was not clear.

Russia's defense ministry, in its daily report of events over the previous 24 hours on Thursday, said air defenses had shot down two British Storm Shadow cruise missiles.

Ukraine fired U.S. ATACMS missiles into Russia on Tuesday after U.S. President Joe Biden gave the all-clear to use such missiles, two months before he leaves office and Donald Trump returns to the White House. Russian President Vladimir Putin on Tuesday lowered the threshold for a nuclear strike in response to a broader range of conventional attacks.

Trump has said he will end the war, without saying how, and criticized billions of dollars in aid for Ukraine under Biden. The warring sides believe Trump is likely to push for peace talks – not known to have been held since the war's earliest months – and are trying to attain strong positions before negotiations.

Moscow has said repeatedly that the use of Western weapons to strike Russian territory far from the border would be a major escalation in the conflict. Kyiv says it needs the capability to defend itself by hitting Russian rear bases used to support Moscow's invasion.