Protesters broke into the construction site of a large Microsoft data centre on the edge of Amsterdam on Friday, during a demonstration against the project.

About 100 people made it onto the site, a Reuters witness said.

A spokesperson for the activist group Geef Tegengas told local broadcaster AT5 that about 500 people had entered the site, while hundreds more stayed outside.

Some of the protesters got in by breaking through a fence, and some climbed a construction crane. Riot police were sent to the site, near Sloterdijk in the city’s western port area, and made several arrests, AT5 reported.

Earlier in the morning, police had stopped the march on its way to the site. The mayor then banned the demonstration, and protesters tried to break through the police line, Dutch news agency ANP reported.

Geef Tegengas, which campaigns against fossil fuels, wants construction of the data centre to stop. The group says the site will use as much electricity as every household in Amsterdam combined and will slow the building of 30,000 new homes.

The organisers also accused the police of behaving badly and said the right to protest had been ignored.

Microsoft had not commented publicly at the time of writing.

The project, which Microsoft will rent in full, consists of three buildings, each 85 metres tall. Plans were first filed in 2016, before Amsterdam banned new data centres within the city, so the provincial government allowed it to go ahead in January, DutchNews reported.

Critics say the project gets around the Dutch rules on very large data centres. At the same time, city officials have warned that shortages on the power grid threaten plans for new homes and schools.

The site has been targeted before; in July, Extinction Rebellion activists threw balloons filled with acid and paint over its fence, as local opposition to data centres grows across Europe and the US.

Friday’s protest was part of two days of action against data centres planned in several European countries on November 6 and 7.