"Xena: Warrior Princess" actress Lucy Lawless and a group of Greenpeace activists boarded an oil-drilling ship in New Zealand Friday in a bid to disrupt plans to search for oil off Alaska.

Lawless and six other protesters boarded the ship Noble Discoverer early Friday in a bid to prevent it sailing to the Arctic, where it has been contracted by Anglo-Dutch energy giant Shell to conduct exploratory drilling.

Lawless said her actions, which temporarily forced authorities to close the North Island port of Taranaki, were prompted by a desire to save one of the world's last pristine environments.

She was not concerned at the prospect of being arrested over the demonstration, in which protesters climbed a drilling derrick on the ship and displayed banners.

"That's the least of my concerns," she told AFP by mobile phone from the ship. "I'm a true believer. We need to start switching over to renewable energy now, we don't have to go to the ends of the earth to suck out every last drop of oil."

New Zealander Lawless, who starred as the title character in the fantasy television series "Xena: Warrior Princess" from 1995-2001, is a long-time environmental activist who was named as a Greenpeace ambassador in 2009.

A Greenpeace spokeswoman said Friday evening that police had made a failed attempt to scale the derrick and the protesters remained on the ship.

She said Lawless and the rest of the group had enough supplies to stay in place for several days and were determined to prevent the ship setting sail for Alaska.

Police said the activists were "clearly breaking the law by trespassing on the ship" but safety was the paramount issue in dealing with the protest.

"Police have agreed an approach whereby the protestors will be left in situ at this stage," they said in a statement, adding officers were on standby to respond to any developments.

The US Interior Department granted Shell conditional provisional approval to begin drilling exploration wells in the Arctic Ocean last August, in a move slammed by conservationists as "inexcusable".

US officials had pledged to closely monitor Shell's plans for four shallow water exploration wells in Alaskas Beaufort Sea to ensure operations are conducted in "safe and environmentally responsible manner".

But green groups say it puts wildlife and native communities in the remote region at risk, citing the vastly complicated task of drilling in the harsh Arctic environment and effectively cleaning up any spills in such conditions.

They also point to the environmental catastrophe in the Gulf of Mexico in 2010 after Shell's Deepwater Horizon rig exploded as an example of the risks inherent in drilling for oil in sensitive areas.