Images show Russian word for 'children' painted outside shelled Mariupol theatre

Vladimir Putin’s forces bombed a makeshift shelter being used by up to 1,200 civilians – including sick children – in a deliberate attack, Ukrainian authorities have claimed.

As the Ukraine crisis rages on, the Mariupol Drama Theatre is now a scene of devastation following the shelling.

Anger sparked by the alleged Russian attack – which Moscow has denied responsibility for – has been magnified by satellite imagery taken of the building on Monday showing that the word ‘children’ painted in Russian on the grounds outside – in a possible sign to bombers not to target it.

The civilians had sought safety in the theatre amid Russia’s three-week siege of the strategic Azov Sea port city.

Ukraine’s foreign ministry said on Thursday morning that there are a number of people trapped inside the theatre, with the number of deaths currently not known.

However, MP Dmytro Gurin, whose parents are trapped in the city, told the BBC: "Minutes ago we had an information that the bomb shelter survived and people there survived. We don't know yet whether we have wounded people, or killed people. But it looks like most of them have survived and are ok."

Ukrainian officials say the central part of the building has collapsed, burying large numbers of people under rubble, while the debris also reportedly blocked the entrance to the bomb shelter located inside the building.

Rescuers are unable to reach the site to stage any rescue efforts due to the continued shelling of residential areas in the port city of Mariupol.

The ministry have now accused Russia of a war crime but Moscow has denied targeting civilians, instead accusing the Azov Battalion, a far-right Ukrainian militia, of blowing it up, according to the RIA news agency.

Watch: Starmer: Mariupol theatre bombing is 'tragic and appalling'

Foreign Office minister James Cleverly said the attack on the theatre “looks to be specific targeting of civilian infrastructure” and a “self-evident breach of international law”.

Asked on ITV’s Good Morning Britain whether the attack on the besieged Ukrainian city amounted to a war crime, Cleverly said: “The targeting of civilian infrastructure, the targeting of civilians is a breach of international humanitarian law and the law of armed conflict.

“So making sure that we collect evidence like we’ve just seen on the programme and other instances is incredibly important so that those people who are responsible for these, whether they are battlefield commanders, right up to the top of the organisation, can be held accountable once this war is concluded.”

Pressed on whether he thought the bombing of the shelter “looked like a war crime”, Cleverly replied: “Ultimately it is for international courts and tribunals to make the formal decision but self-evidently, this is civilian infrastructure which we’ve seen had the word ‘Kids’ painted in Russian outside of this building.

“This looks to be targeting, this looks to be specific targeting of civilian infrastructure and, as I say, that is a self-evident breach of international law and the law of armed conflict.”

The bombing comes the week after Russia targeted a maternity hospital in Mariupol, killing at least three people – including a six-year-old child.

Ukrainian president Volodymyr Zelenksyy has condemned the attack on the theatre, saying: “My heart is broken because of what Russia does with our people.”

Speaking after the bombing, Petro Andruishchenko, an adviser to the mayor of Mariupol, told CNN that the theatre was the city's largest shelter “in number and size”.

He added: “More than a thousand people were hiding there but the probability of getting there to dismantle the rubble is low due to constant shelling and bombing of the city.”

Meanwhile, the Ministry of Defence (MoD) said Ukraine was continuing to have success in “stalling Russia’s advance”, with the Kremlin’s forces also “struggling to overcome the challenges posed by Ukraine’s terrain”.

There has also been a “failure to gain control of the air”, the department said, in its latest defence intelligence update.

“The tactics of the Ukrainian armed forces have adeptly exploited Russia’s lack of manoeuvre, frustrating the Russian advance and inflicting heavy losses on the invading forces,” the MoD tweeted.

Defence secretary Ben Wallace, speaking during his visit to Nato’s headquarters in Brussels, said weapons from Western nations are still reaching Ukrainian forces on the front line.

He said members of the alliance need to “see what more we can do” to support Ukraine’s defence against Russia’s incursion.

Elsewhere, Britain is one of six nations calling for a United Nations Security Council meeting on Ukraine on Thursday, ahead of an expected Friday vote on a resolution demanding protection for Ukrainian civilians “in vulnerable situations”.

“Russia is committing war crimes and targeting civilians,” the UK’s UN mission tweeted, announcing its joint plea alongside the US, France and others.