NSW police officers have arrested 15 people after removing Greenpeace climate change protesters hanging off the Sydney Harbour Bridge this morning.

Three members of the environmental group used cables to suspend themselves below the bridge about 5:30am.

NSW Police said a "number of people" on the bridge as part of the protest this morning were detained by security personnel, but three were able to climb it.

The three unfurled banners on climate change.

The ABC understands the protesters were unable to unveil a bigger banner planned for the protest after security personnel stopped the other activists on the bridge this morning.

The protest continued until about 9:00am when police removed the last of the three from the bridge, lowering them to a police boat waiting underneath.

One of the Greenpeace activists being removed from the Sydney Harbour Bridge ( ABC News )

Traffic on the bridge was flowing and all lanes remained open during the protest.

Police were at the scene directly above the three protesters.

Speaking on this morning's protest, Prime Minister Scotto Morrison said taking action on climate was "important", but said protesters needed to be considerate of others.

Labor leader Bill Shorten said he did "not approve".

"I feel for the emergency officials who have to put themselves on the line to get these people down," he said.

Greenpeace said the three were "specialist trained climbers" and were joined by protesters on the ground nearby.

"Rural and regional Australian families have borne the brunt of climate impacts so far in this country," Greenpeace Australia Pacific chief executive David Ritter said.

"Burning coal is the number one cause of climate change in Australia — we're here to say 'no more'."

The 15 people were taken to Surry Hills and Day Street Police stations.

The protesters were charged with: risking safety of another by climbing a structure, wilfully preventing free passage, climbing on the bridge and trespassing.

They were all bailed to appear at Downing Centre Local Court on June 5.

Mr Ritter said the organisation was cooperating with NSW Police.

Greenpeace conducted a similar protest marking the signing of the Kyoto protocol in 1997.