US President Joe Biden has agreed to give Ukraine anti-personnel land mines, a US defence official told the BBC, a move seen as an attempt to slow Russian troops who have been steadily advancing in Ukraine’s east in recent months.

The official, who was speaking on condition of anonymity, said such mines would be delivered soon and Washington expected that they would be used on Ukraine’s territory.

Ukraine was also committed to not using such mines in densely-populated areas, the official said.

Separately, the US embassy in Kyiv said it had “received specific information of a potential significant air attack on 20 November”.

“Out of an abundance of caution, the embassy will be closed, and embassy employees are being instructed to shelter in place,” it said in a statement.

“The US embassy recommends US citizens be prepared to immediately shelter in the event an air alert is announced.”

The provision of anti-personnel land mines is the latest move by the outgoing US administration to bolster Ukraine’s war effort before Donald Trump returns to the White House on 20 January.

Russia has deployed landmines liberally since the start of its full-scale invasion of Ukraine in February 2022 but international objections to the use of such weapons on the grounds that they pose a risk to civilians had prevented the Biden administration from signing off on them.

The US defence official confirmed to the BBC that Ukraine had pledged to use only mines that remained active for a limited period of time.

The US “non-persistent” mines differ from Russia’s as they become inert after a pre-set period of time – anywhere from four hours to two weeks. They are electrically fused and require battery power to detonate. Once the battery runs out, they will not detonate.

Washington has already been providing anti-tank mines to Ukraine, but the anti-personnel land mines – which can be rapidly deployed – are designed to blunt the advances of ground forces.

Earlier, it was confirmed that US-made longer-range Army Tactical Missile System (Atacms) missiles had struck targets inside Russia only days after reports emerged that the White House had granted permission for their use.

Russia’s defence ministry said the strike had targeted the Bryansk region bordering Ukraine to the north on Tuesday morning.

It said five missiles had been shot down and one had caused damage – with its fragments starting a fire at a military facility.

But two US officials said initial indications suggested Russia had intercepted just two missiles out of around eight fired by Ukraine.

The BBC has not been able to verify independently the contradicting figures.

Russian Foreign Minister Sergei Lavrov accused Washington of trying to escalate the conflict.

The Kremlin has vowed to retaliate.

On Tuesday, Russian President Vladimir Putin approved changes to Russia’s nuclear doctrine, setting out new conditions under which the country would consider using its arsenal.

It now says an attack from a non-nuclear state, if backed by a nuclear power, will be treated as a joint assault on Russia.

Commenting on the changes, US state department spokesperson Matthew Miller said: “Since the beginning of its war of aggression against Ukraine, [Russia] has sought to coerce and intimidate both Ukraine and other countries around the world through irresponsible nuclear rhetoric and behaviour.”