A Greenpeace ship arrived Thursday at the Arctic site where Statoil is sending an oil rig in an attempt to stop the drilling, the environmental group said.

"The Esperanza is a small ship but we are determined to stay on top of this drilling site and stop Statoil," Greenpeace Arctic campaigner Sune Scheller said in a statement.

Greenpeace said the vessel is occupying the exact location where the company plans to drill.

Earlier on Thursday, Norwegian police removed seven Greenpeace activists who boarded the Statoil oil rig in the Barents sea as it made its way to the site.

"The activists on board the Transocean Spitsbergen are now in the hands of Norwegian police," Statoil said in a statement.

The environmentalists were part of a group of 15 activists who on Tuesday boarded the oil rig, which is due to drill the Scandinavian country's northernmost well in the Hoop area of the Barents Sea.

The drilling site is near Norway's Bear Island, which is part of the Svalbard archipelago and has been a nature reserve since 2002.

Receding ice in the Arctic caused by global warming is making drilling possible in areas that were out of reach only decades ago.

"The activists are standing up for the Arctic and Bear Island," Greenpeace activist Scheller said.

"They want to save this pristine and harsh environment from oil spills."

According to Greenpeace, the activists are from Denmark, Finland, Norway, the Philippines and Sweden, and among them was a Finn who spent two months in prison in Russia for a similar action in September last year.

The NGO said they were questioned by police in Norway and then freed.

"The removal happened peacefully, and Transocean Spitsbergen is now moving towards the drilling site a few hours further north," Greenpeace said on their release.

The seven activists removed on Thursday were the last to leave the rig, after five were voluntarily helicoptered to land and three decided to return to the Greenpeace ship Wednesday.

Statoil has accused the NGO of acting "irresponsibly and illegally", and said the organisation has been told of "the risk associated with actions against a rig in open waters".

The rig is registered on the Marshall Islands, which asked Norway to assist in the removal of the activists, according to a statement from Norwegian police.

Greenpeace has filed a complaint against the project and the Norwegian Ministry of Climate and Environment still has to decide if drilling can go ahead in the Hoop field.