Two Greenpeace activists have been charged after sailing out to open waters and occupying an offshore gas platform to protest Woodside's planned gas developments.

In a joint statement, the Australian Border Force, WA Police and the national offshore petroleum regulator NOPSEMA said 48-year-old man and a 52-year-old man had been charged with "interfering with offshore petroleum installations or operations".

They said the offence carried a maximum penalty of 10 years' imprisonment.

The men are due to face Karratha Magistrates Court today.

Footage shared by Greenpeace showed activists sailing out to the Scarborough gas rig about 200 kilometres off WA's coast on Saturday morning, scaling the infrastructure and unfurling a large banner with the words "stop Woodside's dirty gas".

The banner also said "save Scott Reef", which is near where Woodside is proposing to develop its $48.7 billion Browse gas project and tap into Australia's largest undeveloped gas resource.

Authorities said they were still investigating the incident.

The proposed Browse development has been hotly contested by environmental groups opposed to new gas projects.

Greenpeace Australia Pacific CEO David Ritter said yesterday the organisation and other advocacy groups had been scaling up their activism in the face of growing community concerns.

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