When there is a threat of incoming Russian missiles in Ukraine, a familiar voice is heard by millions, warning them to take cover.

Mark Hamill, the actor who played Luke Skywalker in Star Wars, recently lent his voice to the Air Alert app, linked to Ukraine's air defence system.

"Attention. Air raid alert. Proceed to the nearest shelter," he says.

"Don't be careless," Mr Hamill's voice continues. "Your overconfidence is your weakness."

It signs off by saying: "The alert is over. May the Force be with you."

The app kicks in when air raid sirens start blaring across the country.

The actor said he decided to lend his voice to the app after admiring the Ukrainian resistance to Russia's invasion last year, which he said evoked comparisons with Star Wars.

"A fairy tale about good versus evil is resonant with what's going on in Ukraine," Mr Hamill told The Associated Press.

"The Ukrainian people rallying to the cause and responding so heroically... It's impossible not to be inspired by how they've weathered this storm."

He is also raising funds to buy reconnaissance drones for Ukrainian forces, partly by selling signed Star Wars posters.

The Air Alert app was co-developed by Ukrainian security systems manufacturer Ajax Systems.

More than 14 million people have already downloaded the app.

"For Star Wars fans, it sounds really fantastic," one user, Hrytsenko, who uses the English-language setting, told AP.

"It's kind of a Ukrainian mentality to find some humour even in the bad situation or to try to be positive."

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