More than 20 people face domestic terrorism charges in Atlanta after they were arrested during violent clashes between officers and protesters at a police training centre construction site, authorities said on Monday.

The 23 people who face charges were part of a group detained on Sunday by police who said they launched bricks, Molotov cocktails and fireworks at officers after they breached the construction site in a wooded area outside Atlanta.

The planned Atlanta Public Safety Training Centre, dubbed “Cop City” by opponents, has been the scene of escalating confrontations between demonstrators and police.

Demonstrators oppose what they call the increasing militarisation of police and say that building the 85-acre training centre would involve cutting down so many trees that it would be environmentally damaging.

Surveillance footage provided by the City of Atlanta Police Department showed what appeared to be police officers trying to lock a gate as fireworks exploded around them.

Other clips appeared to show protesters throwing rocks over a fence, several small fires burning at the site and heavy construction equipment on fire.

Atlanta police chief Darin Schierbaum said pieces of construction equipment were set on fire in what he called “a coordinated attack” at the site.

It is unclear if any of the people have been formally charged by the DeKalb County District Attorney, whose office was not immediately available for comment.

Almost all of those arrested are from around the US, while one is from Canada and another from France, police said.

The police and fire training centre is being built on 85 acres of a 400-acre property in DeKalb County that is owned by the city.

It is within the larger South River Forest and opponents of the site say they want to save an important green space near the greater Atlanta metropolitan area.

Sunday’s events began with a music festival that was part of a week of demonstrations against the construction site and in support of police reforms. A group broke off from the concert to start a protest.

In January, the site was subject to a protest which briefly turned violent.