By Dan Satherley and Kim Choe
Police have told protesters aboard the Noble Discoverer – including actress Lucy Lawless – they are under arrest.
Lawless and five others are protesting from atop the derrick on an oil exploration ship in Port Taranaki, trying to stop it leaving for the Chukchi Sea off the coast of Alaska where it is due to search for oil deposits.
"They came up just to talk to us as a courtesy to say, "You are under arrest, we suggest that you come down," and we said, "No, we do understand that, thankyou so much for your concern, we feel we have no choice morally but to stay here and get our message out," Lawless told RadioLIVE.
Greenpeace New Zealand revealed the protest this morning on its Twitter account.
"BREAKING: Lucy Lawless and five Greenpeace climbers have boarded an Arctic-bound @Shell oil drillship in Port Taranaki -More soon."
The group scaled the 53-metre drilling derrick on the Noble Discoverer around 7am. The ship, operated by Shell, is bound for the Chukchi Sea off the coast of Alaska.
"Our main aim is that this be a peaceful protest, but the law will do what the law has to do," Lawless told 3 News,
"We do what we feel we have to do."
One person, not aboard the ship, was arrested at the port's gates.
Lawless says she joined the protest "on behalf of the planet and my children".
“Deep-sea oil drilling is bad enough, but venturing into the Arctic, one of the most magical places on the planet, is going too far. I don’t want my kids to grow up in a world without these extraordinary places intact or where we ruin the habitat of polar bears for the last drops of oil.”
Lawless tweeted at around 9:10am, "All safe up here but a squall coming in. Good spirits."
The protesters apparently have enough provisions to last at least three days. Banners reading "Stop Shell" and "#SaveTheArctic" have been hung from the ship.
"The first half hour after getting up I was shellshocked, my mouth was dry, I just couldn't believe we weren't intercepted," says Lawless.
"But we weren't... so we just continued along our merry little way. But I was kind of in shock."
Greenpeace says if Shell finds oil there, it will spark "an Arctic oil rush".
"Freezing temperatures, unpredictable weather and remote drilling locations pose unprecedented challenges, making an oil spill impossible to contain and clean up," says Greenpeace campaigner Steve Abel.
Shell says it is "disappointed" with Greenpeace's actions.
"Actions such as this jeopardise the safety of everyone involved," the company said in a statement.
"While we respect the right of individuals to express their point of view, the priority should be the safety of Noble Discoverer’s personnel and that of the protestors."
Port Taranaki harbour master John Ireland earlier told RadioLIVE there are no Arctic-bound ships in port.
"I can categorically state that we have no Arctic-bound drill ships in the port," he told RadioLIVE.
The port has since been closed, and Mr Ireland was last reported to be in discussions with police.
Lucy Lawless aboard the Noble Discoverer (Greenpeace)
Last year the Xena: Warrior Princess, Spartacus and Battlestar Galactica star urged Kiwis to sign a petition calling for a ban on offshore drilling in New Zealand.
"I'd urge anyone who wants to protect our coasts from an even worse oil spill than that which we saw in Tauranga to sign this petition," she said in November.
"By doing so, they'll also be doing something positive about the climate crisis that this planet is facing."
In 2009 Lawless and climate scientist Jim Salinger tried to deliver a cheque to Prime Minister John Key to pay for his flight to the Copenhagen climate change talks, after he decided not to go.
They were stopped by Parliament security.