The announcement of the transfer of the 28 activists and two journalists was unexpected and without explanation, The New York Times reported. Greenpeace said it was not aware of the reason.
The activists' ship was seized in September after several onboard attempted to climb an offshore oil rig, owned by the Russian state-run oil and gas company Gazprom, in the Arctic Sea, the Russian news agency RIA Novosti reported Friday.
They were initially charged with piracy, and later with hooliganism.
"All 30 people were charged with hooliganism. The previous charges of piracy have not been lifted," said Greenpeace Russia spokeswoman Maria Favorskaya Friday, prior to the announcement of the transfer.
"Families and consular officials will now find it easier to visit the 30," said Kumi Naidoo, Greenpeace International's executive director. "But there is no guarantee conditions inside the new detention center (in St. Petersburg) will be any better than in Murmansk."
Russian authorities said Oct. 23 the initial piracy charges would be dropped, RIA Novosti reported, adding the activists' defense team will appeal the charges after the International Tribunal for the Law of the Sea rules on the issue Nov. 6.