A protest by refugee activists has raised concerns about security at Prime Minister Tony Abbott’s Sydney electorate office.

Four people were arrested on Monday morning after using a ladder to climb onto the roof of the building in Manly, on Sydney’s northern beaches, where they unfurled a banner protesting the detention of asylum seekers.

It’s understood the group is linked to refugee activists who disrupted the Australian Open men’s tennis final on Sunday night after jumping onto the court at Rod Laver Arena, and another protest on Monday morning that delayed a Qantas flight from Melbourne to Darwin.

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The two men and two women who spent about two hours on the prime minister’s office roof, are now facing trespassing charges.

They were arrested when they came down from the roof, with police describing the protest as peaceful.

However, the ease with which the four activists, aged in their 20 and early 30s, were able to make their way onto the roof has raised security concerns, with NSW Police saying the issue would be raised with the Australian Federal Police.

“But you can rest assured the electoral office of the Prime Minister and other important buildings like that are regularly patrolled,” Inspector Graeme Pickering told reporters.

It’s understood the protesters are from the group, Cross Border Collective.

Banner above @abbottmhr office in Manly @smh. Protestors climbed across rooves in the rain! pic.twitter.com/zrWuDmhmqZ

— Nick Beaugeard (@nickbeau) February 1, 2015

Refugee-policy protesters on roof of Tony Abbott’s Manly office right now; helicopter hovering overhead pic.twitter.com/v3vdqljvhx

— Emily Wilson (@emilyhwilson) February 1, 2015

The group says on its Facebook page the co-ordinated action and its campaign, Hunger for Justice, was organised to express solidarity with detainees on Manus Island, Nauru and in detention in Darwin.

One of the activists, Claire Parfitt, said the Manly protest was to show solidarity with 15 refugees on a hunger strike in Darwin including one man, Martin, who she said was close to death.

The same group is understood to have disrupted the Australian Open final for at least five minutes, forcing the players off the court, and raising security concerns.

“We have created this international media spectacle today to expose the torture, abuse, and horrific conditions that are being perpetrated on Manus Island,” the group said.

It’s believed they also delayed a Qantas flight on Monday morning.

The flight was reportedly delayed by about 50 minutes after several passengers refused to sit down in protest over the recent deportation of a Tamil asylum seeker.

“The passengers refused to follow cabin crew instruction so were offloaded and met by the Australian Federal Police,” a Qantas spokeswoman said.

Former Manly NRL player Anthony Watmough weighed into the issue saying police should use rubber bullets on the protesters.

“clowns protesting in man(l)y do u not Realise your stupid action are hurting other peoples business I hoped the police use rubber bullets on u! (sic),” he tweeted on Monday.

Watmough, who has now signed with Parramatta, then sent another tweet: “U will achieve nothing. I hope the people u have affected today get reimbursed from your own wallet its not cheap to own a business u idiots.”

-AAP