An international tribunal has ordered Russia to pay damages and costs of nearly 5.4 million euros ($6.2 million) to the Netherlands for unlawfully seizing a Greenpeace ship protesting at an oil platform in Arctic waters.

The Arctic Sunrise, sailing under a Dutch flag, was seized by Russian authorities in September 2013 during a protest against an offshore oil platform. The 30 people on board were arrested and detained for months before eventually being released shortly before the Sochi Olympics.

The five-member panel, based in Vienna, decided in 2015 that Russia was liable under the U.N. Convention on the Law of the Sea and has now put a price on damages to the ship, as well as the wrongful arrest and suffering of 30 people aboard.

Russia declined to take part in the proceedings.

Greenpeace International's General Counsel, Jasper Teulings, says the ruling "emphatically upholds international law and the right to peaceful protest against oil drilling in the Arctic."