Ukraine fired a number of British Storm Shadow cruise missiles into Russia’s Kursk region on Wednesday, a day after firing American long-range missiles into the country, according to Pentagon and Ukrainian officials.

Moscow has said that the use of Western weapons to strike deeper into Russian territory is a major escalation, and for months that stance had kept the United States and Britain from allowing Kyiv to use the American long-range missiles or the Storm Shadows.

But President Biden last week authorized the first use of the American Army Tactical Missile Systems, known as ATACMS, deep inside Russia. American officials say the pivot was in response to Moscow’s surprise decision to bring North Korean troops into the fight. Prime Minister Keir Starmer of Britain quickly followed suit, authorizing Ukraine to use the Storm Shadows, officials said.

Britain had previously allowed Ukraine to use the missiles against Russian positions within Ukrainian territory.

Storm Shadows have a range of more than 150 miles, so they give Kyiv the ability to hit targets deeper into Russia.

Downing Street declined to comment on Wednesday, saying it could not speak about operational details. Asked about it in Parliament, John Healey, Britain’s defense secretary, said: “We have seen, over recent weeks, a significant change in the action and in the rhetoric on Ukraine, and Ukraine’s action on the battlefield speaks for itself. We, as a nation and as a government, are doubling down on our support for Ukraine, and are determined to do more.”