MONTREAL -- Dozens of vaccination appointments are being rescheduled or moved to other clinics Saturday due to a protest being planned at the Olympic Stadium in Montreal. 

The regional health authority said approximately 50 appointments are affected at the Big O, one of the city's largest vaccination sites. 

The CIUSSS de l'Est-de-l'Ile-de-Montreal said it already had limited doses available and once it learned about the protest a few days ago, it stopped offering appointments for Saturday. The vaccination centre will be closed at 10 a.m. due to the protest and will re-open Sunday. 

Some Saturday appointments will be moved to the morning at the stadium, while others will be moved to the Martin Brodeur Arena in St-Leonard or the Centre Roussin in Pointe-Aux-Trembles.

According to a Facebook event, the "Quebec Debout" group is organizing a demonstration at noon at the stadium. A press release from the groups claims thousands of people are expected to "make history" in a protest against public health measures in the province that are aimed at curbing the spread of COVID-19.

The Montreal protest is one of several planned for May 1 throughout Quebec. 

On Friday, Quebec's health minister, Christian Dube, said it was "extremely unfortunate" that appointments will have to be moved to other clinics to accommodate the people who are being affected. 

Prime Minister Justin Trudeau told reporters the planned protest is "deeply disappointing." Freedom of speech and assembly are important, especially during a pandemic, but protests must be done safely, he added.

"The irony here is that by gathering, people are putting each other at risk, spreading further cases of COVID-19, and extending the time in which we will have to be faced with restrictions and public health measures," Trudeau said.

On Thursday, Quebec announced it is opening up its mass vaccination campaign to the general public in a gradual roll-out in the coming weeks.

-- With files from The Canadian Press