President Vladimir Putin has confirmed that Russia tested a hypersonic intermediate-range missile in an assault on the Ukrainian city of Dnipro, Ukraine.

The Kremlin said the attack was in response to Ukraine’s recent use of US- and UK-supplied missiles to target Russian territory.

Joe Biden, the outgoing US president, and his administration only recently gave the green light for Ukraine to launch long-range strikes into Russia, a move which has escalated tensions.

The Pentagon said the US had been notified of the launch through nuclear risk reduction channels.

Here is what you need to know:

What is the Oreshnik, Russia’s new ballistic missile?

The new intermediate-range ballistic missile, Oreshnik, which means hazel tree in Russian, is a nuclear-capable weapon that has not been previously mentioned publicly.

The Pentagon said it is based on the “RS-26 Rubezh” intercontinental ballistic missile (ICBM).

Hypersonic missiles travel at speeds of at least Mach 5 – five times the speed of sound – and can manoeuvre mid-flight, making them harder to track and intercept.

The missile can have three to six warheads, military expert Viktor Baranets wrote in the Komsomolskaya Pravda tabloid.

Igor Korotchenko, editor of the Moscow-based National Defence journal, told the TASS state news agency that based on video footage of the strike, Oreshnik has multiple independently guided warheads.

Why has Russia used this missile now?

Russia is in retaliation mode.

The launch came after Ukraine fired US- and UK-supplied missiles on Russian territory for the first time, escalating tensions in the nearly three-year-long conflict.

This followed the reversal of a ban on Kyiv, which had been placed by Washington, on using high-precision Army Tactical Missile Systems (ATACMS) to strike targets in Russia.

Moscow says six US-made ATACMS missiles were launched at Russia on Tuesday, while British Storm Shadow cruise missiles and US-made HIMARS were fired at the country on Thursday.

Moscow says this makes Western countries that authorise Ukraine to use their missiles to hit Russia direct participants in the conflict.

Kremlin spokesman Dmitry Peskov said on Friday that Moscow was in “no doubt” that Washington had understood that the strike on Dnipro was a warning.

“The main message is that the reckless decisions and actions of Western countries, which produce missiles, supply them to Ukraine, and subsequently take part in carrying out strikes on Russian territory, cannot remain without a reaction from the Russian side,” Peskov said.

What has Putin said about the attacks?

In an unscheduled television appearance on Thursday, Putin said the strike on the city of Dnipro had tested in combat conditions “one of the newest Russian mid-range missile systems”.

Putin said it had been deployed “in a non-nuclear hypersonic configuration” and said the “test” had been successful and had hit its target.

Putin said air defences cannot intercept the Oreshnik.

“Modern air defence systems… cannot intercept such missiles. That’s impossible,” Putin said.

“As of today, there are no means of counteracting such a weapon,” the president boasted.

Putin also stated that Russia will “address the question of further deployment of intermediate and shorter-range missiles based on the actions of the United States and its satellites”.

What has Ukraine said about the strike?

Kyiv claimed that Russia had used an intercontinental ballistic missile (ICBM) along with a barrage of other missiles at Dnipro.

Local authorities said the attack hit an infrastructure facility and injured two civilians.

President Volodymyr Zelenskyy warned of a “clear escalation”.

An intercontinental ballistic missile (ICBM) has a range of 1,000-5,500km (621 to 3,418 miles), a level below that of an intermediate-range ballistic missile.

Ukraine’s Main Intelligence Directorate said it was fired from the 4th Missile Test Range, Kapustin Yar, in Russia’s Astrakhan region and flew 15 minutes before striking Dnipro.

The missile had six warheads, each carrying six submunitions. The peak speed the missile reached was 11 Mach.

What happens next?

NATO will hold an emergency meeting with Ukraine at the alliance headquarters in Brussels on Tuesday to discuss Moscow’s use of the missile, a NATO source said on Friday.

The Western military alliance confirmed that the NATO Ukraine Council, grouping allies’ NATO ambassadors and their Ukrainian counterparts, will convene at Kyiv’s request, but did not give any detail on the topic of discussions.