The passage of the Mikhail Ulyanov tanker, carrying first oil from Prirazlomnaya, was yesterday blocked by the Rainbow Warrior.

Rainbow Warrior captain Peter Willcox was also part of the Arctic 30 group, whose members were released from Russian prison just prior to the Sochi Winter Olympics.

Dutch police boarded the Greenpeace ship after Willcox ignored orders to move out of the tanker's way.

Another 30 activists were detained for trespassing or blocking the Mikhail Ulyanov on rubber rafts.

All in all, two ships plus a fleet of rubber rafts, paragliders and activists onshore were involved in the incident, in which the slogan "No Arctic oil" was painted on the hull of the Mikhail Ulyanov.

Mikhail Ulyanov captain Stanislav Chichin told energy news website FuelFix that the action violated "fundamental principles of international conventions for safety at sea as well as environmental safety".

"Manoeuvring in the confined waters of a port is no less dangerous than sailing in the Arctic, especially when another vessel is trying to interfere with a tanker transporting 67,000 tonnes of crude oil in an area of high-intensity shipping," he said.

In March Greenpeace launched a case against the Russian Federation in the European Court of Human Rights on behalf of its Arctic 30 activists, claiming that they were detained unlawfully.