A festive march through downtown Montreal on Tuesday marked the official opening of the World Social Forum (WSF), which is being held for the first time in a G7 nation to try to bridge a north-south divide.

As many as 5,000 people took part in the walk, singing and dancing in the streets, and waving placards, including one that read: "I can't believe I still need to protest for the environment and justice."

Far from southern Brazil where the first WSF was held in 2001, the 12th edition of the anti-globalization conference is expected to have the lowest attendance ever.

But organizers refused to concede this was a sign that the movement is in crisis.

"It's wrong to say that the World Social Forum is fizzling out," said organizers Carminda Mac Lorin, pointing to a growing number of regional WSF meetings around the world.

A delegate from Guinea who took part in the opening march, however, questioned how the event could be considered international if most of the participants this year hail from Canada and other rich northern nations.

"I don't see many Africans here today," Fatoumata Cherif of Women Power and Development (WOPOD) told AFP.

"We talk about the World Social Forum, but if there are only participants from the northern countries I do not see how this would be the World Social Forum."

Canadian aboriginal activist Jocelyn Iahtail welcomed the chance to take part in the summit only a two-hour drive from her home in Ottawa.

"It's definitely an opportunity that the event is here in Canada," she said.

The WSF's goals have evolved over the years, with the fight against globalization overtaken by more mainstream concerns of both rich and poor nations, such as tax evasion, climate change or the plight of refugees.

The organizers of the 2016 WSF hope to bridge what they described as a rich-poor, north-south divide in order to find solutions together to the world's woes.

- Coming together -

"We must overcome the divide between north and south... social inequalities are increasing everywhere," said Raphael Canet, an organizer of the 2016 WSF.

Brazilian activist and WSF co-founder Chico Whitaker noted that many social ills are endemic to all peoples.

"The problems that we face in the third world are felt in industrialized countries too," said the former leftist politician who is now engaged in environmental causes.

Several workshops on global warming have been scheduled throughout the six-day summit, including a talk moderated by Canadian activist and "No Logo" author Naomi Klein. Participants will also debate the plight of an increasing number of refugees displaced by conflicts and disasters, as well as income inequality and fair trade.

Organizers said they chose to hold this year's event in Montreal in order to showcase the city's vibrant civil society, but higher relative costs for travel and accommodations meant many foreign delegates could not attend.

More than 230 guests were also denied entry by Canada, including Mali's former culture minister Aminata Dramane Traore and Palestinian postal union president Imad Temiza.

Canadian immigration officials blamed WSF organizers for failing to inform the ministry's special events unit of difficulties in obtaining participants' visas.

"We did everything we could, we're not bureaucrats," Canet said, noting that the visa application process was "long and arduous and costly."