The mayor of Vancouver has issued a warning to people participating in Saturday's Occupy Vancouver protests, saying that violence will not be tolerated.

Gregor Robertson said he respects the right of people to demonstrate peacefully in the protest, planned to start at 10 a.m. tomorrow in front of the Vancouver Art Gallery.

He believes the vast majority of participants plan to participate in the event for the right reasons, but says there is a risk of the demonstration being hijacked by people with other intentions.

"We know from our experience with the Stanley Cup riots and the protests that marked the start of the Olympic Games that large gatherings can sometimes attract small groups of people determined to use these avenues for their own violent ends," Robertson said in a statement issued to media Friday.

There will be a large police presence, he added, and the city will do what it can to make sure that people have "the ability to be heard safely, and that this protest is not undermined by violence or destructive behaviour of any kind."

"Senior City staff are working closely with the VPD and stakeholders across the community to ensure we are positioned to support a lawful and peaceful protest," Robertson said.

Vancouver police are also worried about the presence of troublemakers hiding in plain sight.

"Experience has shown us that any large gathering of people can serve as a cover for those with a different and unlawful agenda," said Const. Jana McGuinness.

Event organizers are working closely and constantly with police to ensure participants will be kept safe, she added.

The VPD is encouraging participants not to wear masks or hide their faces, saying anyone doing so could face additional charges if they cause any violence.

McGuinness said although the Occupy protests have remained largely peaceful, police are well prepared if "the larger group" commits any crimes, or riots.

Police have issued several warnings to businesses in the downtown core to be prepared for the protests to spread.

"This movement is non-violent and is not known to encourage property damage, but the VPD advises that you prepare for any eventuality," read a memo sent out Thursday.

"The VPD is taking appropriate precautions and preparing to ensure a safe protest for everyone involved."