Actress Salma Hayek was among several stars to hold up placards in solidarity with the Bring Back Our Girls campaigns.
The viral hashtag is in support of the Nigerian schoolgirls who were kidnapped by Islamic insurgents Boko Haram almost a month ago.
French actress Julie Gayet also held up a sign during a photocall on the red carpet arriving for the Tribute to animated films at the Cannes Film Festival.
The Nigerian military has flown more than 300 sorties in the hunt for the abducted schoolgirls, a Major has told ITV News' Rageh Omaar.
A newly released video from Boko Haram reportedly shows the kidnapped Nigerian schoolgirls.
The man who started a viral hashtag campaign in support of the kidnapped Nigerian schoolgirls says it has forced the government to act.