About 100 protesters reportedly showed up on Park City's Main Street for a protest organized by "Let Gaza Live" ... with police in the small Utah town shutting down the block to traffic.

Among those protesting ... former 'Scream' star Melissa Barrera -- who was fired for her comments on the war between Israel and Hamas -- and model/actor Indya Moore.

MB kept a low profile with her hood on and sunglasses covering her eyes while IM was more front and center ... at one point using a megaphone at the rally.

BTW, Barrera's been talking a lot about her firing recently ... telling the Associated Press Friday night that getting laid off from the popular franchise was a "big awakening" for her adding she's "grateful" for everything that's happened.

The protest was pretty peaceful all morning ... with videos populating social media of passionate protesters -- though their chants stirred up some controversy.

Some of the protesters used the phrase "From the river to the sea" which is a point of contention between Israel supporters and Palestine supporters ... they're also going right after President Biden calling him "Genocide Joe" and repurposing an old condemnation of Lyndon B. Johnson -- asking him how many kids he's "killed today."

Protesters in support of Israel were also on the streets in Park City ... seemingly mounting a counter-protest and chanting "Bring them home" in reference to hostages taken by Hamas during the tragic October 7 attack.

It should be noted that the protest was not affiliated with Sundance, instead just running near it ... a move other political protesters have used in the past to capitalize on media attention. Thousands of protesters gathered back in 2017 to protest then-newly inaugurated President Trump.