According to a number of witnesses in Bucha, fléchette rounds were fired by Russian artillery a few days before they withdrew from the area at the end of March.

Svitlana Chmut, a resident of Bucha, told the Washington Post she had found several nails on her car.

‘Uncommon and rarely seen’ weapon

Although human rights groups have long sought a ban on fléchette shells, they are not prohibited under international law.

According to Neil Gibson, a weapons expert at the UK-based Fenix Insights group, who has reviewed the photos of the fléchettes found in Bucha, the metal darts came from a 122mm 3Sh1 artillery round, in use by Russian artillery.

Mr Gibson said fléchettes were an “uncommon and rarely seen projectile”.

In a Twitter post, he said the weapon was the Russian equivalent of the US “Beehive” series of anti-personnel projectiles, so-named because of the apparent buzzing of the darts as they flew through the air.

Major Volodymyr Fito, a spokesperson for Ukrainian land forces command, said the Ukrainian military did not use shells with fléchettes.