The International Tribunal on the Law for the Sea in Hamburg ruled on Friday that Russia must release the Arctic Sunrise icebreaker and all 30 people on board on bond of €3.6 million ($4.8 million).

The release is a provisional measure: the maritime court still has to rule on the legality of Russia seizing the vessel.

Russia said earlier it does not accept the court’s authority in the case because of exceptions the country made when ratifying the UN’s Convention on the Law of the Sea in 1997.

Ivanov reaffirmed Russia’s dismissal of the tribunal.

“The question will be solved on a judicial, not political plane, [and] based on Russian legislation, not someone’s political wishes,” the Kremlin official said.

The Kremlin said on Saturday that 30 Greenpeace crew members held after a protest in Arctic waters could be allowed to leave Russia, but the international activist group greeted the statement warily.

"As soon as the issue of how they can leave Russia is resolved they will leave," Kremlin Chief of Staff Sergei Ivanov said, according to a RIA-Novosti agency report.

"Nobody will hold them," he said.

Ivanov did not elaborate, but Interfax news agency reported that the issue hindering the crew members' departure is their lack of Russian visas.

The crew were seized by Russian security forces off a Greenpeace ship in the Barents Sea after a September protest on a Gazprom oil rig, brought to Russia and charged in Russian courts with piracy, later reduced to hooliganism. All but one of the activists have been granted bail.

It was the first time since the beginning of the affair in mid-September that a high-ranking Russian official has suggested the foreigners of 16 nationalities making up the Greenpeace crew could leave Russia.

Ivanov's comments came after an international maritime court on Friday ordered Russia to immediately release the crew and their Dutch-flagged ship in exchange for a 3.6-million-euro ($4.9-million) bond.

Russia says it does not recognise the court as having a right to rule on the matter.