The temporary office set up by Greenpeace in the Russian city of Murmansk was broken into on Thursday night, the environmental organisation said on Friday.
Video footage shows six people in balaclavas entering the building. They reportedly stole a cage which the organisation was planning to use as part of a protest action on Friday.
Judges in Murmansk will today decide if Dutch activitist Faiza Oulahsen should be remanded in custody on piracy charges. On Thursday, another Dutch activist, Mannes Ubels, failed in his bid to be released.
The two Dutch nationals are part of a group of 30 activists arrested last month when Russian coastguards seized their ship Arctic Sunrise which was campaigning against Gasprom drilling in Arctic waters.