"Proud of my kids and all the kids for stepping up today," tweeted Stiller.

"These kids are awesome," MacFarlane said of protesters at Marjory Stoneman Douglas High School in Parkland, scene of the 14 February shooting.

Fourteen students and three members of staff died in the attack, the deadliest US school shooting since 2012.

Wednesday's protests saw tens of thousands of pupils across America demand action on gun control.

Students left classes at 10:00 local time for 17 minutes - one minute for each person killed in Parkland.

"Respect to all those kids in America staging there [sic] walkout," tweeted singer Liam Gallagher. "Enough is enough."

Comedian Amy Schumer, meanwhile, called on people to take part in March For Our Lives, another US-wide protest taking place on 24 March.

Others to voice support for the students included Golden Globe winner Rachel Brosnahan, who said she was "so moved and inspired" by the nationwide action.

Singer Rufus Wainwright was among other celebrities to praise the coordinated protest, encouraging pupils to "keep marching" and "keep speaking out".

The same sentiments were expressed by Charmed actress Alyssa Milano, who called on politicians to "listen to the youth leading the way".