Lucy Lawless and six other Greenpeace activists have been released from police custody this afternoon after they were arrested for spending three days on a Shell oil ship.

The protesters were arrested this morning and descended the rig of the Shell-chartered Noble Discoverer around 12pm.

Greenpeace said they considered the action to have been hugely successful.

"When we started this seven of us went up the rig but 133,000 came down with us in solidarity. They're writing letters and we know that new heros are going to spring up in our fervent mission to make sure the oil industry becomes an energy industry is one that is renewable and clean," Lawless said.

The protesters have been bailed to appear in the New Plymouth District Court on Thursday, when they will face charges of burglary.

Actress Lucy Lawless and five other Greenpeace protesters were arrested after spending four days on board the Noble Discoverer, which was due to travel to the Arctic in exploration of oil.

Lawless and a group of Greenpeace activists scaled the ship's 53-metre drilling derrick and unfurled banners in Port Taranaki at 7am on Friday.

The ship was scheduled to leave the port yesterday to drill three exploratory oil wells in the Chukchi Sea off the coast of Alaska, but the journey was delayed due to the protesters' actions.

Lawless' involvement drew international attention to their cause.

The police climbed the tower this morning to speak with the protesters, and subsequently arrest them. They did not resist.

Lawless, before being arrested, said the battle to save the Arctic had just begun.

Over the course of the occupation, more than 133,000 people sent an email to Shell executives telling them to cancel their plans to drill in the Arctic, causing Shell email systems to overload repeatedly, Greenpeace claimed.

Police said it was too early to say when the protesters, including Lawless, would appear in court.

Steve Abel, a Greenpeace climate campaigner, who was at the Taranaki port, said it was one of the longest lasting occupations in recent history in New Zealand."

"If there was an oil spill in the Arctic it would be impossible to clean up," Abel said. "This is what this is about."

THE PROTEST SAGA

Shell earlier rejected claims by protesters that it "bombarded" them with loud screams and sounds played over the speakers on the drill-ship Noble Discoverer.

Lawless last night said from the ship that Shell was "going Guantanamo on us".

"They've upped the ante. Shell are getting pretty pissed off, what one could expect."

The protesters were being "bombarded" with the persistent booming sounds from loud speakers, including screams and feedback sounds, she said.

"It's making us howl with laughter. It's going to be a bumpy night."

But a spokeswoman for Shell said the sounds had not been made in response to the protesters, but were just standard procedure.

Normal operations involve work throughout the day and night, she said.

"As part of routine work standard procedure requires the crane's horn to be sounded when the crane moves over the vessel. There was no loud music or other extraneous noise."

- © Fairfax NZ News