Russia has reportedly used banned munitions to shell parts of Ukraine - but what are cluster bombs and why would using them class as a war crime?

According to reports in the Daily Mail and Independent, cluster bombs were used to attack civilian areas in the east of Ukraine, where many locals have fought back against Vladimir Putin's invasion.

A military source told MailOnline that one video circulating online showed the Russian military bombing a shopping centre in the Serpnia area with 'cluster' munitions.

Here's what you need to know about cluster bombs.

The Herald: Mykhailo Makarov from Ukraine and living in Dublin protests at the entrance to the Embassy of Russia in Dublin where prior to his arrival red paint was poured on the coat of arms of the Russian Federation following the Russian invasion of Ukraine. Photo via PA.Mykhailo Makarov from Ukraine and living in Dublin protests at the entrance to the Embassy of Russia in Dublin where prior to his arrival red paint was poured on the coat of arms of the Russian Federation following the Russian invasion of Ukraine. Photo via PA.

What is a cluster bomb and how does it work?

According to the organisation Cluster Munition Coalition, a cluster munition or cluster bomb is a weapon containing multiple smaller explosive devices.

Cluster bombs are dropped from aircraft or fired from the ground or sea, opening up in mid-air to release tens or hundreds of smaller munition devices, with the ability to attack an area up to the size of several football fields.

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Are cluster bombs a war crime?

The unknown military source told the MailOnline that cluster bombs are a "war crime" when "used against civilians".

The newspaper's source said: "The BM-21 Grad is a multiple launch rocket system used for 'area denial', dropping cluster bombs on a concentrated area.

"It's mainly used on enemy troops before an offensive. Used against civilians, it's not only a war crime, but has only one purpose – to spread terror and alarm among the civilian population."

Ukraine has now accused Russia of war crimes during the invasion over the bombardment of civilian areas in the second city, Kharkiv.

The Kremlin has denied that the Russian military used cluster munitions in Ukraine and insisted that the Russian forces only have struck military targets.

Kremlin’s spokesman Dmitry Peskov insisted that “the Russian troops don’t conduct any strikes against civilian infrastructure and residential areas”.

Mr Peskov’s claim contradicts abundant evidence documented of indiscriminate shelling of homes, schools, and hospitals across Ukraine.

Mr Peskov also rejected the accusations that the Russian military has used cluster munitions and devastating vacuum weapons - dismissing them as fabrications.

Speaking in a conference call with reporters, he would not respond to questions about whether the Kremlin is happy with the pace of the offensive and would not comment on Russian military casualties.

The Russian defence ministry said for the first time on Monday that it has suffered losses but did not name any numbers.