Russia said Wednesday it had reduced piracy charges against the detained crew of Greenpeace's Arctic Sunrise protest ship to "hooliganism", which carries a lesser sentence.

The Investigative Committee said it had "taken the decision to reclassify the crime as hooliganism".

Russia early this month charged all 30 crewmembers of Greenpeace's Arctic Sunrise protest ship with piracy after they attempted to scale a state-owned oil platform in a protest against drilling in the Arctic.

The piracy charge against the crewmembers, who come from 18 different countries, attracted international criticism.

They faced up to 15 years in prison if found guilty of piracy, while the new charge carries a maximum sentence of seven years in a penal colony.

All 30 are being held in prison pending trial after Russian border guards towed their ship to the northern city of Murmansk.

The Committee said the crew were charged with acting in a group and with "using objects as weapons".

Russia also charged the Pussy Riot punks with hooliganism after they carried out a peaceful protest against President Vladimir Putin in a Moscow church.

Three of the Pussy Riot members were sentenced to two years in a penal colony.