THE HAGUE (AFP) - The Dutch police on Thursday boarded a Greenpeace ship in Rotterdam harbour as it tried to stop a Russian tanker delivering oil drilled in the environmentally fragile Arctic.

"The police are on board, they're trying to tow us away," Greenpeace activist Willem Wiskerke tweeted from on board the Rainbow Warrior, which had tried to prevent Russian tanker Mikhail Ulyanov docking.

Rotterdam police confirmed to AFP that they were involved but could not immediately provide further details.

Greenpeace said a group of 80 activists backed by the Rainbow Warrior had been trying to prevent the tanker docking, having painted "No Arctic Oil" in large letters on the tanker's hull.

"Activists in inflatables are trying to prevent the ship from mooring by putting themselves between the quay wall and the tanker," Greenpeace said in a statement.

The Rainbow Warrior is captained by Mr Peter Willcox, who was among campaigners detained by Russian authorities last year after staging a high-profile protest against Arctic drilling.

The oil on board the Russian tanker is the first to be delivered from the Prirazlomnaya platform, an offshore rig owned by Russian energy giant Gazprom and the site of Greenpeace's protest last September.

That protest, which saw two campaigners attempt to scale the rig, prompted the Russian authorities to seize Greenpeace's Dutch-flagged Arctic Sunrise boat and detain the 30 activists and journalists on board.

Greenpeace argues that the Gazprom rig is an environmental catastrophe waiting to happen that risks ruining the pristine Arctic ecology of the southern Barents Sea where the deposit is located.

The activists had faced lengthy prison terms before Moscow announced amnesties.

The Rainbow Warrior set off on Monday to confront the tanker, but the Russian vessel switched off its satellite tracking equipment.