MOSCOW (AP) — Activists say that police have detained several participants in a protest against the construction of a waste dump in northwestern Russia.

Several thousand demonstrators rallied in Arkhangelsk on Sunday demanding the project be halted, and some have vowed to stay on the city's central square to press their demands.

Police allowed the unsanctioned protest to go on peacefully, but detained several organizers on Monday, according to OVD-Info, an independent online portal monitoring human rights issues.

Regional Gov. Igor Orlov, who has faced criticism for stonewalling complaints against the waste plant, has criticized the demonstrators for failing to get official clearance for the protest.

The rally in Arkhangelsk was the latest in a series of protests in Russia focusing on environmental issues, such as toxic landfills and waste processing plants.