Oscar winners Jared Leto and Penelope Cruz were among the famous faces posting messages of solidarity to the people of Ukraine during a “chaotic and disruptive time” for the country.
In heartfelt statements, Hollywood stars prayed for the safety of family and friends and a peaceful resolution to the conflict.
It comes as violence continues to escalate in the region following attacks ordered by Russian president Vladimir Putin, which have targeted cities and bases in Ukraine.
The Ukrainian government said 137 civilians and military personnel had been killed after the first day of fighting.
House Of Gucci star Leto urged his family and friends caught up in the “devastating” conflict to stay “as safe as you can”.
“To my friends and family in Ukraine – my heart breaks that this conflict has escalated in such a devastating way,” he wrote.
“Please take great care and be as safe as you can. Sending thoughts to you and your loved ones during this chaotic and disruptive time.
“I’m hopeful that peace will prevail and nonviolent solutions will ultimately be found.”
Cruz, who is also nominated for best actress at this year’s Academy Awards, posted an emotional plea for peace on behalf of the children of Ukraine.
Sharing a Unicef post, she wrote in Spanish: “More than nothing else, what the children of Ukraine need now is peace.
“No child, wherever they are born, grow up or live, should know violence and the atrocities of conflict.
“Millions of children in Ukraine were woken up today in the middle of the night by the sound of explosions.
“They should be our priority.”
Avengers star Mark Ruffalo also sent his support to Ukrainian young people caught up in a “sad and corrosive moment of asymmetrical violence and destruction.”
“You have done nothing to deserve this perversion and obscene spectacle,” the Hulk actor wrote.
Lord Of The Rings star Elijah Wood added: “My heart is with Ukraine and its people.
Gene Simmons, co-lead singer of rock band Kiss, wrote on Twitter: “Our hearts and minds are with the brave people of Ukraine.
“You are not alone!”
Meanwhile, American singer Barbra Streisand revealed that her paternal grandparents emigrated from Ukraine.
On Twitter, the 79-year-old said: “My heart breaks for the courageous people there fighting this Russian invasion.
“Putin’s propaganda about ‘denazification’ as a rationale is one of the great lies of this Century.”
As the fighting began Ukrainian president Volodymyr Zelensky declared martial law and called on citizens to volunteer to fight for their country.
Former heavyweight champion boxer, and mayor of Kyiv, Vitali Klitschko, was among those answering the call, saying that he had “no other choice but take up arms”.
In an interview with ITV, Klitschko said Vladimir Putin had “totally” lost his sense of reality by starting a “bloody war.”
Genesis musician Peter Gabriel also blasted the Russian president and his “barbaric decision” to invade.
“Very shocked to see so many Ukrainians being killed, a totally unnecessary war being deliberately started in Europe,” the musician said.
“This action is a war crime, and whatever else happens, he should never be allowed to leave Russian soil again.”
The conflict is thought to be Moscow’s most aggressive action since the Soviet invasion of Afghanistan in 1979.
Leaders of the 30 Nato allied nations will meet on Friday to hammer out how next to push back against the “cynical and brutal invasion,” described by Prime Minister Boris Johnson as a “dark day in the history of our continent”.