CANNES, France -- When Salma Hayek walked the Cannes Film Festival red carpet holding up the sign "Bring Back Our Girls," the cast of "The Expendables" followed suit the next night -- even if some of them didn't know what the slogan was about.
"I remember Victor (Ortiz) was like, 'What were those signs?' and I had to fill him in,'" actor Kellan Lutz of his co-star.
Ortiz, Hayek and others helped spread the message, a plea for the return of nearly 300 girls kidnapped in Nigeria by the Islamist extremist group Boko Haram, by using one of the most famous media events in the world. The "Bring Back Our Girls" campaign has become a hashtag on Twitter and championed by luminaries including U.S. first lady Michelle Obama.
Still, it wasn't the only social message at Cannes this year. The actors and director of the Turkish film "Winter Sleep" held up signs reading "Soma," referring to the recent Turkish mining tragedy that killed 301 miners.
In an interview with The Associated Press this week, Angelina Jolie, known for her activism, worried that stars promoting the "Bring Back Our Girls" campaign could backfire.
"We need to not turn the Boko Haram into superstars that get more attention for doing something so horrible," she said. "We need to go after them, arrest and they need to face justice.
"Because at the end of the day, the bigger picture is this kind of horror happens around the world. Women are facing this kind of abuse, so are men and boys. And the answer cannot be simply one situation and that will solve it."
"I would beg the media, for all of us, to not treat things one at a time," she added.
Other stars were supportive of using the Cannes stage to promote something more serious than films.
Actor Viggo Mortensen, who held up a flag of his soccer team at his Cannes photo call for the movie "Jauja," had no problem with other celebrities doing the same for something weightier.
"I have no problem speaking out when it seems appropriate or called for -- I've done it before," he said.
Hayek held up the sign as she walked the red carpet for her animated film "The Prophet." She said it was not out of character.
"I was always involved in women's rights before I was a celebrity," she said. "But of course (the premiere) was a good opportunity to use it to continue to put pressure on the governments so that they bring back our girls."
Lutz said the "Expendables" cast were handed the signs before they walked the carpet but he was already supportive of the campaign.
"To do it on one of the most watched locations and spots where people in the films are just walking up, and it's just such an iconic location ... it impacts so much," he said.