Greenpeace has complained of a disproportional use of force after heavily armed and masked Polish border guards bordered one of the organisation’s vessels moored off the port of Gdansk in a night-time raid.

Video released by the environmental campaign group shows the guards in special-forces-style uniforms and equipped with automatic weapons smashing cabin windows with sledgehammers while ordering the crew to put their hands up and lie on the ground.

The ship, the Rainbow Warrior, has been in Gdansk blocking the unloading of coal from a Mozambique cargo ship. Greenpeace is protesting against Poland’s continued reliance on coal as an energy source. Last year, the group says, Poland imported around 20 million tons of coal despite the environmental costs associated with the fuel.

“We believe that we have the right to peaceful protest, we were in touch with the authorities telling them we are peacefully protesting against the further use of coal,” Katarzyna Guzek, from Greenpeace Poland, told The Telegraph.

“We were very surprised to see armed guards and the disproportionate measures taken against the people on board Rainbow Warrior. We are a peaceful organisation so we were surprised by what happened.”

Marek Jozefiak, a co-ordinator of Greenpeace Poland’s climate and energy campaign, said that it was “unacceptable” that activists had been “threatened with machine guns”.