Ukraine has fired long-range British Storm Shadow missiles into Russian territory for the first time, a day after launching United States-made long-range missiles into the country, British media outlets report.

Russian war correspondent accounts on Telegram posted footage on Wednesday they said included the sound of the missiles striking in the Kursk region, which lies on Ukraine’s border. At least 14 huge explosions can be heard, most of them preceded by the sharp whistle of what sounds like an incoming missile. The footage, shot in a residential area, showed black smoke rising in the distance.

People in Kursk also reportedly found fragments from the missiles in the region.

A spokesperson for British Prime Minister Keir Starmer said his office would not be commenting on reports or operational matters.

Britain had previously said Ukraine could use Storm Shadow cruise missiles within Ukrainian territory, but London has been pressing Washington for permission to allow their use to strike targets inside Russia for several months.

On Tuesday, Ukraine used US-made long-range weapons to strike targets in Russia. US President Joe Biden’s administration has allowed Kyiv to use these missiles in and around the Kursk region only.

Afterwards, Russian President Vladimir Putin lowered the threshold for a nuclear strike in response to a broader range of conventional attacks. Washington said afterwards it had not seen any reason to adjust its nuclear posture while China called for restraint.

In another US policy shift on Wednesday, Biden authorised the use of antipersonnel landmines in Ukraine. Washington also announced a $275m military aid package for Ukraine, including ammunition for the High Mobility Artillery Rocket System (HIMARS), artillery shells, Javelin surface-to-air missiles, and small arms and ammunition.

The US policy shifts come as Russia’s war in Ukraine, which has been ongoing for more than 1,000 days, is at a volatile juncture. Nearly a fifth of Ukrainian territory is in Russian hands. North Korean troops are deployed in the Kursk region, and there are growing doubts over the future of Western aid as US President-elect Donald Trump prepares to return to the White House in January.

Reporting from Kyiv, Al Jazeera’s Assed Baig said the decision to authorise the use of antipersonnel landmines is likely in line with a US attempt to help Ukraine slow down Russian advances in its east to gain more leverage in future peace talks.

“The Biden administration is on its way out, and we have President-elect Donald Trump coming into office, who has criticised US military aid to Ukraine and has also said he would end this war in a matter of days,” Baig said.

“So what the US administration wants is to put Ukraine in a very strong position to at least slow down some Russian advances so that when there are negotiations, Ukraine is put in a more advantageous position than what it is now,” he added.

The US is not a signatory to a 1997 convention banning landmines, but Biden had pledged to limit their use.

The Russian government said Washington’s actions show the US wants to prolong the war, and it has promised to respond.

Russian foreign intelligence chief Sergei Naryshkin warned in an interview published on Wednesday that Moscow would retaliate against NATO countries that facilitate long-range Ukrainian missile strikes against Russian territory.