The Netherlands has started legal action to free 30 crew members of Greenpeace's Arctic Sunrise - including two New Zealanders - charged by Russia with piracy after a protest against Arctic oil drilling.
"The Netherlands, as the state under whose flag the Arctic Sunrise sails, today started an arbitration process on the basis of the UN Convention of the Law of the Sea," Foreign Minister Frans Timmermans said in a letter in parliament.
The action is against what the Netherlands sees "as the unlawful detention of the ship (and) to have it released and its crew freed", Timmermans wrote.
Dutch Foreign Ministry spokesman Friso Wijnen said the Netherlands believed the crew's arrest was illegal as Russia should have first asked Dutch authorities' permission to board the ship.
Russian investigators have charged all Arctic Sunrise crew members with piracy, an offence that carries a prison sentence of up to 15 years. A court in the northern city of Murmansk last week remanded the crew members in custody for two months, including freelance journalists, pending an investigation into their mid-September protest on an oil platform owned by energy giant Gazprom.