The United States believes Russia fired a never-before-fielded intermediate-range ballistic missile on Thursday in its attack on Ukraine, an escalation that analysts say could have implications for European missile defences.

Here’s what we know so far about the missile.

What kind of ballistic missile is it?

The US military said the Russian missile’s design was based on the design of Russia’s longer-range RS-26 Rubezh intercontinental ballistic missile (ICBM).

The new missile was experimental and Russia likely possessed only a handful of them, officials said.

The Pentagon said the missile was fired with a conventional warhead but that Moscow could modify it if it wanted.

“It could be refitted to certainly carry different types of conventional or nuclear warheads,” Pentagon spokesperson Sabrina Singh said.

Jeffrey Lewis, a non-proliferation expert at the Middlebury Institute of International Studies in California, said the Russian president, Vladimir Putin, had earlier hinted that Russia would complete the development of an intermediate-range ballistic missile (IRBM) system after Washington and Berlin agreed to deploy long-range US missiles in Germany from 2026.

“The RS-26 was always [a] prime candidate,” Lewis said.

Singh said the new variant of the missile was considered “experimental” by the Pentagon. “It’s the first time that we’ve seen it employed on the battlefield ... So that’s why we consider it experimental.”

US and UK sources indicated that they believed the missile fired on Dnipro was an experimental nuclear-capable, intermediate-range ballistic missile (IRBM), which has a theoretical range of below 3,420 miles (5,500km). That is enough to reach Europe from where it was fired in south-western Russia, but not the US.

Ukraine’s air force initially said the missile was an ICBM. While launching an IRBM sent a less threatening signal, the incident could still set off alarms and Moscow notified Washington briefly ahead of the launch, according to US officials.

Will Russia’s missile strike affect Nato?

Timothy Wright, at the International Institute for Strategic Studies, said Russia’s development of new missiles might influence decisions in Nato countries regarding what air defence systems to purchase as well as which offensive capabilities to pursue.

A new US ballistic missile defence base in northern Poland has already drawn angry reactions from Moscow. The US base at Redzikowo is part of a broader Nato missile shield and is designed to intercept short- to intermediate-range ballistic missiles.

Still, Putin said Thursday’s launch of the new IRBM was not a response to the base in Poland but instead to recent Ukrainian long-range strikes inside Russian territory with western weapons.

After approval from the administration of President Joe Biden, Ukraine struck Russia with US-made Atacms on 19 November and with British Storm Shadow missiles and US-made Himars on 21 November, Putin said.

What has Vladimir Putin said about the new missile?

The Russian president acknowledged in a television address to the nation that Moscow had struck a Ukrainian military facility with a new ballistic missile and said it was called “Oreshnik” (the hazel).

He said its deployment “was a response to US plans to produce and deploy intermediate and short-range missiles”, and that Russia would “respond decisively and symmetrically” in the event of an escalation.

Moscow said it targeted a missile and defence firm in the central Ukrainian city of Dnipro, where missile and space rocket company Pivdenmash, known as Yuzhmash by Russians, is based.

Putin said Russia was developing short- and medium0range missiles in response to the planned production and then deployment by the US of medium- and shorter-range missiles in Europe and Asia.

“I believe that the United States made a mistake by unilaterally destroying the treaty on the elimination of intermediate-range and shorter-range missiles in 2019 under a far-fetched pretext,” the Russian president said, referring to the intermediate-range nuclear forces (INF) treaty.

The US formally withdrew from the 1987 (INF) treaty with Russia in 2019 after saying that Moscow was violating the accord, an accusation the Kremlin denied.