Diana Berg, who lives next to the theatre but managed to escape the city before the bombing, told Sky News: “I know that there were pregnant women that were brought from the maternity ward in the third hospital that was bombed the days before.

“They were brought to the theatre because it was a big building and they put these pregnant women with kids in the dressing rooms for actors. It was in this part that was bombed. They were in the theatre, right at exactly the point where it was hit. That’s what we know.”

Satellite photos released by Maxar Technologies showed the Russian word “children” clearly written in large script on the ground in front and behind the building.

Ms Berg also told Sky News that there are now so many bodies in Mariupol it is impossible to bury them – and that some are hanging from trees. The 300 victims are likely to be buried in mass graves across the city.

No emergency services are operating in Mariupol because constant shelling makes it impossible to enter, which prevented rescue attempts from the theatre.

It took survivors hours to escape, with 150 people pulling themselves from the rubble in the immediate aftermath.

The attack is believed to be the worst single atrocity in a European war for more than a quarter of a century. It has prompted calls for General Mikhail Mizintsev, the man accused of coordinating the aerial attack, to face war crimes.