Frozen star Idina Menzel has applauded a young Ukrainian girl after a video went viral online showing the youngster singing 'Let It Go' in a bunker amid Russia's invasion.

Marta Smekhova, who shared the sweet video on Facebook on March 3, had visited the bunker to help decorate it last week, The Independent reports. Smekhova explained at the time that the young performer, Amelia, told her she dreamed of singing on a "grand stage".

The colors blue and yellow, representing the Ukrainian flag, could be seen behind the girl as she sang the iconic Disney song, which received a round of applause. She performed the Frozen track in her native language.

"From the first word in the [shelter] came complete silence… everyone put their business aside and listen[ed] to a song by this girl who was just beaming light… even men couldn’t hold back the tears." Smekhova wrote in the lengthy caption, according to a translation by Deadline.

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After seeing the emotional clip, Idina Menzel - who voiced Elsa, the character who performs the song in Frozen - took to Twitter on Sunday night to share: "We see you. We really, really see you."

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Smekhova explained in the caption of the original post that the video was filmed and shared with the permission of the girl's mother. Smekhova added: "Amelia, sweetheart, you are our Ukrainian star."

Those in the shelter were reportedly seeking protection in the unknown location in Kyiv during the Russian invasion.

The Academy Award-winning song 'Let It Go' was originally recorded by Menzel for the 2013 Disney animated movie Frozen. It was written by Kristen Anderson-Lopez and Robert Lopez.

The song became a hit worldwide, with Disney releasing the compilation Let it Go: The Complete Set in 2014, which included 22 performers singing the song in 41 languages.

More than a million people have now fled Ukraine nearly two weeks after Russian President Vladimir Putin announced plans for a "special military operation" in Ukraine, according to a UN report.

If you would like to know how you can support the Ukrainian people at this time, click HERE to find a list of organizations and groups dedicated to helping those affected by this crisis.

Featured image credit: JEP Celebrity Photos / Alamy

Idina Menzel responds Ukrainian girl singing 'Let It Go' in bunker shelter