Key Points:

Three peace activists, accused of deflating one of Waihopai spy base's domes with sickles today, have been remanded in custody on criminal damage and burglary charges.

But police told Blenheim District Court they were considering charging the men with sabotage under the Crimes Act, an offence which carries a maximum sentence of 10 years' jail.

Damage to the Marlborough base, run by the Government Communications Security Bureau (GCSB), is estimated at more than $1 million.

Samuel Peter Frederick Land, 24, of Hokianga, Adrian James Leason, 42, a teacher from Otaki and Peter Reginald Leo Murnane, 67, a Dominican friar from Auckland, have all been charged with intentionally damaging a satellite, the property of the GCSB, and entering a building with the intention to commit a crime.

At today's bail hearing, Judge Richard Russell remanded Leason and Murnane in custody without plea to reappear in court on Monday. Land's bail application was adjourned until Monday and he was also kept in custody.

The three men were arrested early this morning, after allegedly using bolt cutters to cut through three security fences and one of two 30-metre domes covering satellite interception dishes was deflated.

They were part of a group called Anzac Ploughshares which aims to spread the message of disarmament by disabling warplanes and military equipment. The group's name comes from a biblical reference to turning swords into ploughshares.

Described as a satellite communications monitoring facility, opponents of the base say it is part of Echelon, the worldwide network of signals interception facilities run by American and British intelligence agencies and contributes to the war in Iraq.

As they were taken from the court into the police van, Land said he was going on a five-day hunger strike, and Leason said he would pray for those in Iraq, where one million people had died, the Marlborough Express reported.

"The war in Iraq takes some explaining," Murnane said.

GCSB deputy director for corporate services Hugh Wolfensohn told the Express the attack had caused more than $1 million damage, but the base was still operating.

"There's been no significant reduction in work. Obviously there's been some (reduction) because we've got an antenna out of action."

He did not know when repairs would take place.

GCSB director Bruce Ferguson told Radio New Zealand the activists had penetrated three fences before deflating the dome. Alarms were activated when the dome was contacted but CCTV footage was no help due to heavy fog, he said.

"I think it was exquisitely good timing for them, rather than planning, in that respect," he said.

Air Marshal Ferguson said the security breach was "deeply disturbing" and remedial measures would be put in place to ensure it did not happen again.

Two two-metre cuts were sufficient to deflate the dome. Then the activists ran around the base of the aerial randomly slicing at other areas, he said.

The domes, made of a rubberised material, acted purely as a "waterproof jacket" to protect the antennae from adverse weather.

A Ploughshares spokesman, Manu Caddie, said planning the attack on the base involved a lot of texting, emails and phone calls, which were not intercepted.

"I guess it shows that the system doesn't work that well."

But Air Marshal Ferguson said the GCSB Act of 2003 specifically forbade targeting of New Zealanders or New Zealand permanent residents.

"We are in the business of collecting foreign intelligence ... satellite collection is there to collect foreign intelligence for the briefing and use of the New Zealand Government," he said.

Prime Minister Helen Clark condemned the attack "as a senseless act of vandalism".

She said the Government had received no comment from other countries regarding the breach.