Climate protesters have blockaded a bridge in central Melbourne with police moving in and arresting multiple people.

Organisers from the Extinction Rebellion movement promised to shut down the Princes Bridge near Flinders Street station from midday.

More than 300 activists descended upon the bridge to call for action around the climate emergency.

“The seriousness of the global climate crisis demands mass non-violent, disruptive action to get the kind of urgent change we need if we want to avoid catastrophe,” spokeswoman Miriam Robinson said.

“We know this type of action is inconvenient for some and we don’t set out to disrupt people’s lives needlessly,” she said.

Victoria Police formally warned protesters twice that if they did not move they would be arrested, before public order officers started to arrest people.

Dozens were arrested and searched at the scene. One womansaid she received a summons for “sitting on a bridge”.

Police including mounted officers blocked both sides of the bridge and prevented members of the public from crossing.

The media were prevented from the accessing the bridge because of “safety concerns”.

People had a right to protest peacefully without affecting the rest of the community, said a police spokeswoman.

“Police have common law powers to prevent a breach of the peace, including but not limited to separating rival groups, preventing access to an area and restraining or detaining people until the peace is restored,” she said.

Diversions remained in place in the area.