US President Joe Biden has announced the country will supply cluster munitions to Ukraine to help its fight against Russian forces.

So what are the devices and why is the decision controversial?

FactCheck takes a look.

What are cluster munitions?

A cluster munition is a bomb that opens in the air and releases smaller “bomblets” across a wide area. It’s designed to take out tanks and troops, and hit multiple targets at the same time.

Why is the decision to give cluster munitions to Ukraine controversial?

Mr Biden’s administration said it will send thousands of cluster munitions to Ukraine as part of a new military aid package worth $800m (£630m).

The munitions are controversial because they have had a high “dud rate” in previous conflicts, which means that some fail to explode initially and then thousands of the smaller unexploded bomblets remain behind, only to injure or kill people years later.

They were last used by the US in 2003 during the Iraq war, but the country decided to stop using them when the conflict moved to more urban environments with higher civilian populations.

There’s actually a 2008 treaty, named the Oslo Convention on Cluster Munitions, which bans the use of cluster bombs. Some 120 countries – including the UK – are signatories, agreeing not to produce, transfer or use these weapons.

Though the US, Russia and Ukraine haven’t joined the pledge. And according to non-governmental research organisation Human Rights Watch, both Russia and Ukraine are already using cluster munitions in the war.

But the United States’ National Security Adviser, Jake Sullivan, claimed to reporters on 7 July that the US-made shells that will be provided to Ukraine have a much lower failure rate.

He also said Ukraine’s government has committed to removing these munitions after the war, which could help prevent civilians from harm by unexploded bomblets.

What has the UK said about cluster munitions?

Referring to the Oslo accord, Prime minister Rishi Sunak told reporters on 8 July that the UK is a “signatory to a convention which prohibits the production or use of cluster munitions and discourages their use”.

He added: “We will continue to do our part to support Ukraine against Russia’s illegal and unprovoked invasion, but we’ve done that by providing heavy battle tanks and most recently long-range weapons, and hopefully all countries can continue to support Ukraine.”

Spain has spoken out on cluster munitions, with defence minister Margarita Robles telling reporters during a rally in Madrid: “No to cluster bombs and yes to the legitimate defence of Ukraine, which we understand should not be carried out with cluster bombs.”

Germany’s foreign minister, Annalena Baerbock, said that the country opposes sending cluster munitions to Ukraine, as does Canada, whose government said in a statement: “We do not support the use of cluster munitions and are committed to putting an end to the effects cluster munitions have on civilians – particularly children.”