At least 150 people have died after a massive tremor hit off the coast of western Sumatra on Monday and triggered a terrifying tsunami.
The disaster intensified when a volcano on the island of Java erupted just hours after the waves hit, killing at least 25 more, while hundreds of others are thought to be missing.
Cruise has led the celebrity tributes to those affected, writing on his Twitter.com page, "Our hearts go out to the people of Merapi & Jakarta Indonesia."
Bieber wrote on his own page, "Just found out about the earthquake in Indonesia. Everyone please pray for the people there."
Other stars to reach out to the victims include The Jonas Brothers - both Nick and Joe Jonas 'Tweeted' "Pray for Indonesia", while rocker Joel Madden wrote, "Indonesia I love you be strong", which was then re-posted by his wife Nicole Richie.