GREENPEACE stepped up its protest against oil exploration north of Scotland yesterday by boarding a Norwegian oil rig.

The tactics are the same as those which led to a legal stand-off between Greenpeace and BP after protests west of Shetland last year.

The environmental campaigners claimed they had ''occupied'' the Statoil rig, which was due to carry out oil and gas exploration work off the Norwegian port of Kristiansund, north of Oslo, in the so-called Atlantic frontier area.

The Deepsea Bergen was due to head south towards UK waters when eight activists boarded the rig and attached a survival pod to the side.

Greenpeace spokesman Kalle Hesstvedt said that three protesters would remain on board, adding it was a ''new part of our campaign to get oil companies to switch to developing renewable energy''.

Coastguards were last night said to be heading for the area and Greenpeace claimed they may attempt to impound the group's vessel, the MV Greenpeace.

The protesters are said to have enough equipment, food, water, and solar cells to continue their protest for ''days and maybe weeks''.

A Greenpeace spokeswoman said similar tactics were used to halt work being carried out by the rig Stena Dee last summer. That ended after seven days when the activists had ''made their protest''.

Statoil said the rig was on the northerly part of the Kristin field, which is thought to hold the equivalent of more than 700 million barrels of oil.

In a separate incident, Greenpeace activists in four inflatable vessels tried to hamper operations on board the Arctic Star, which was gathering seismic data in the Alaskan Beaufort Sea for British Petroleum and Exxon.