At least five people were injured at a Chile football stadium on Friday after an advertising structure collapsed under the weight of Colo Colo fans that had climbed on top.

Images shared on social media showed the moment the structure buckled under the weight of dozens of supporters, sending some fans tumbling onto others standing below.

"Emergency under control: the five injured people were treated by personnel" from the emergency services, the fire brigade said on Twitter.

Around 20,000 fans had turned up to Colo Colo's Estadio Monumental David Arellano stadium in Santiago for the team's last training session ahead of Sunday's local derby against Universidad Catolica, the reigning champions.

"We've told them many times, in campaigns, in everything: everyone has to behave themselves," the club's Uruguayan midfielder Maximiliano Falcon said on the Colo Colo Twitter account.

"It's tiring to keep doing it but they still don't (behave)."

Colo Colo lead the standings by 11 points with five matches remaining and could be crowned champions on Sunday with a victory if other results go their way.

With 32 titles they are the most successful club in Chilean football, and also the only one from the country to have lifted the Copa Libertadores, in 1991.