ATLANTA (AP) Police used tear gas and flash-bang grenades Monday to halt a march against building an Atlanta-area police and firefighter training center that opponents call Cop City.

More than 400 people marched about 2 miles (3.2 kilometers) from a park to the site in suburban DeKalb County, chanting stop Cop City and Viva, viva Tortuguita, invoking the nickname of an activist who was fatally shot by state troopers while camping in the woods in protest earlier this year.

A wedge of marchers, including some in masks, goggles and chemical suits intended to protect against tear gas, pushed into a line of officers in riot gear on a road outside the training center site. Officers pushed back and deployed tear gas. One protester threw a canister back at officers.

Protests against the proposed training center have been going on for more than two years. Georgia Attorney General Chris Carr obtained a sweeping indictment in August, using the states anti-racketeering law to charge 61 protesters, characterizing them as militant anarchists.

Protesters called Monday's march Block Cop City and events were held across the country in recent weeks to support the movement. It was the latest effort to stop construction of a project that has galvanized environmentalists and anti-police protesters across the country. Protester Sam Beard, rallying the crowd Monday, said the movement has fused environmentalists and police abolitionists.

We are never letting go of each other again, Beard said. That is what has made this movement powerful. That is what has made this movement dangerous.

Some marchers retreated from the clash while others tried to wash away the effects of tear gas. Dozens of protesters ran into the woods near the property where the training center is being built and exited with their hands up. The marchers eventually retreated as a group without any arrests being made. Vomiting and irritation from the tear gas were the only apparent injuries.

Police agencies including the DeKalb County Police Department and Georgia state troopers were guarding the site, including with armored vehicles.

In a statement, DeKalb County police said the march was not permitted and that protesters refused commands to disperse and clear the roadway.

Atlanta Mayor Andre Dickens and other supporters say the 85-acre, $90 million facility would replace inadequate training facilities and help the police department recruit and retain officers. Opponents say the facility could lead to greater police militarization and that its construction in the South River Forest will worsen environmental damage in a poor, majority-Black area.

Ahead of the march, Kamau Franklin of Community Movement Builders told the crowd they had a duty to practice civil disobedience against the project. Prior to the march, Beard said the activists had been urged not to bring weapons, use incendiary devices or destroy construction equipment.

You are standing up strong and fighting a struggle to stop a militarized complex which is meant to continue to over-police Black and brown communities in this country and is meant to stop movements against police violence and police militarism, Franklin said.

Some protesters in Mondays march had hoped to reoccupy the wooded area that includes the construction site and adjoining park. Activists spent months camping in the woods there until police pushed them out in January. That sweep included the fatal shooting of 26-year-old protester Manuel Esteban Paez Tern, known as Tortuguita.

A prosecutor last month declined to pursue charges against the state troopers who shot Paez Tern, saying the activist shot a trooper and that law enforcement's use of deadly force was objectively reasonable.

Paez Terns parents spoke before the march. Previously, they have said they do not believe authorities version of events and have called for an independent investigation. The family commissioned an autopsy that concluded Paez Terns hands were in the air when the activist was shot.

I see, in each one of them, my son, Belkis Tern told The Associated Press of the crowd. Manuel always said, To fight the police, you have to be happy. So happiness is what we have brought.

Resistance to the project has at times sparked violence and vandalism. Prosecutors now characterize the protest movement as a conspiracy, saying it has led to underlying crimes including possessing fire accelerants and throwing Molotov cocktails at police officers.

Most of those indicted in August on the racketeering charges had already been charged with other crimes in connection with the movement. RICO charges carry a sentence of five to 20 years in prison that can be added on top of the penalty for underlying acts.

Among the defendants are more than three dozen people who previously faced domestic terrorism charges in connection to the protests. Also charged were three leaders of a bail fund previously accused of money laundering ; and three activists charged with felony intimidation. Authorities said they distributed flyers calling a state trooper a murderer for his involvement in Paez Terns death.