Russia moved the crew of a Greenpeace Arctic protest ship from the northern port of Murmansk on Monday and put them on a train to Saint Petersburg, the organisation said.

The 28 activists and two reporters, arrested in September after protesting against oil exploration in the Barents Sea, left their detention centre at 5:00 am (0100 GMT) and are now on a train, said Greenpeace spokeswoman Dannielle Taaffe.

The arrested crew of the ship Arctic Sunrise includes 26 foreigners from 18 countries held for nearly two months on charges of piracy and hooliganism after an attempt to scale an oil platform operated by Russia's energy giant Gazprom.

Greenpeace said that "persistent rumours" from diplomatic sources indicate that all 30 are being transferred to Saint Petersburg, a journey of about 1,500 kilometres (950 miles).

One of Russia's northernmost cities, Murmansk endures polar nights in the winter, with temperatures often dropping to below minus 30 degrees Celsius (minus 22 degrees Fahrenheit).

Several activists in mid-September attempted to scale Russia's Gazprom oil platform in the Pechora Sea, part of the Barents Sea, in protest at the firm's exploration in the Arctic.

Russian authorities boarded the ship on September 19 and towed it to Murmansk. Greenpeace says the authorities had no right to detain the Dutch-flagged ship in international waters.

Russian authorities initially accused the activists of carrying out illegal research, then charged them with piracy. They then changed the piracy charge to hooliganism, an offence that can be punished by a maximum of seven years in prison.

But Greenpeace said the piracy charge was never officially lifted.

Last month, Russian authorities also said the ship carried illegal drugs such as poppy straw and morphine, which Greenpeace denies.

The platform is located in Russia's exclusive economic zone on the Arctic shelf, which means that most Russian laws do not apply there.