Joe Biden has lifted the ban on Ukraine using long-range missiles to fire into Russian territory by permitting them to be used against Russian and North Korean forces in the Kursk region.

The US president will allow Ukraine to use US-made Atacms rockets, which have a range of 190 miles (300km) – a decision being justified by the presence of North Korean troops fighting alongside Russia against Ukraine.

Though there was no public comment from the White House, the story first appeared in coordinated briefings to the New York Times, the Washington Post and the news agencies Reuters and Associated Press.

Ukraine’s president, Volodymyr Zelenskyy, appeared to confirm the news, though he said any proof about the change in policy would emerge on the battlefield, if and when the missiles are used.

“Today, there’s a lot of talk in the media about us receiving permission for respective actions. But strikes are not carried out with words. Such things are not announced. Missiles will speak for themselves. They certainly will,” Zelenskyy said.

Poland’s foreign minister welcomed the news. “With the entry into the war of North Korea troops and the massive airstrike of Russian missiles, President Biden responded in a language that Putin understands,” Radosław Sikorski wrote on X.

But Vladimir Dzhabarov, the first deputy head of the Russian upper house’s international affairs committee, warned Moscow’s response would be immediate.

“This is a very big step towards the start of world war three,” the Tass state news agency quoted Dzhabarov as saying.

It is the first time Biden has given Kyiv permission to use long-range weapons inside Russia but their use will be limited to the Kursk region, where Ukraine launched an incursion into Russia in the summer.

Kyiv announced nationwide energy rationing from Monday after Moscow’s biggest drone and missile attack in months on Ukraine’s energy grid on Sunday.

US officials briefed that the weapons would be used against Russian and North Korean troops deployed against Ukrainian forces in Russia’s Kursk region – and was intended to send a message to North Korea – though Biden may authorize their use elsewhere during his remaining two months in the White House.

The first strikes using US-supplied Atacms rockets could come within days. The decision is not thought to apply to UK-supplied Storm Shadow missiles, the use of which on Russian territory has previously been blocked by the US.

Kyiv has indicated it wants to use Storm Shadows against airbases used to launch attacks on Ukraine, instead of in Kursk. The White House and Downing Street declined to comment.

It is not clear if Donald Trump, who has previously criticized the scale of US military aid to Ukraine, will seek to reverse the decision. Biden previously allowed Ukraine to use shorter-range US-supplied Himars against Russian forces attacking Kharkov from over the border, but had refused permission for deep strike weapons Russia.

Last month, North Korea sent an estimated 10,000 troops to Russia to participate in the Ukraine war, the first time Pyongyang has been prepared to use ground forces since the end of the Korean war in 1953.

They have since been positioned in Kursk and preparing to join with Russian troops in a counterattack against in joint force whose strength is estimated at 50,000.

Other reports, based on Ukrainian intelligence briefings, have suggested that North Korea could be willing to send as many as 100,000 troops if the alliance between the two countries strengthens, at a time when Kyiv is struggling to mobilize more people to join the war.

Earlier on Sunday, the Ukrainian president said about 120 missiles and 90 drones were fired into Ukraine that morning in a nationwide attack he described as the work of “Russian terrorists”.

The attack was the largest missile and drone assault on Ukraine since August and the first big Russian assault since the US election, showing the Kremlin in little mood to compromise after Trump’s victory.