SYDNEY - Military helicopters are set to be deployed to fly onto cruise ships in Australia to test passengers for the coronavirus as more than a dozen ships remained drifting off the coast or docked at ports, carrying an estimated 15,000 passengers.

The federal government has banned cruise ships from docking in Australia. In some areas, armed police have been patrolling the shoreline to ensure ships do not dock.

The New South Wales Police Commissioner, Mr Mick Fuller, confirmed that he wanted the military to assist with sending medical specialists onto the eight ships off the state's coast, which are carrying 8,615 passengers. Most are crew members.

"It would be an extremely large operation," he told The Australian.

"These cruise ships left ports with people in them knowing that coronavirus was active, knowing that prime ministers and premiers had started to warn people - they set sail knowing this risk."

The crackdown follows an incident in which a cruise ship, the Ruby Princess, docked in Sydney two weeks ago with 2,700 passengers, including 13 who had been tested for the virus but were awaiting results. The passengers were allowed to freely disembark without being tested.

It has since emerged that at least 440 passengers were infected, many of whom flew to homes across the country or overseas. At least five of the passengers have since died.

The ship now remains off the coast of Sydney with no passengers but more than 1,000 staff members still aboard. Six have been taken ashore and rushed to hospitals in Sydney with suspected infections.

Carnival Cruises, which owns the Ruby Princess, insists the vessel must stay close to shore in case more crew members need to be taken to hospital.

As of Thursday (April 2) morning, Australia had 5,103 cases of the coronavirus and 23 deaths.

Australia, like other countries, is now grappling with the question of how to handle cruise ships, including several which arrived with infected passengers. Ships remain stranded off the coast across the country.

Earlier this week, Commissioner Fuller ordered the ships off the New South Wales coast to return to their ports of origin.

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"They don't pay taxes in Australia, they don't park their boats in Australia, their primary flags are often in the Caribbean in different islands," he told reporters. "It's time to go home."

In Western Australia, the state government has faced a separate dilemma in dealing with a coronavirus-afflicted German-operated cruise ship, Artania, which is docked at Fremantle port. Forty-one infected passengers from the ship are now being treated at the state's hospitals.

The 850 passengers are largely German, though some are reportedly from Switzerland and Australia. Most were taken ashore, and flew back to Germany on Sunday on chartered flights, aside from 12 who had reported feeling unwell and stayed onboard. They were evacuated on Wednesday to a hotel in Perth.

But there are still about 450 crew members aboard, who have asked to remain in Fremantle for a further two weeks to ensure any infected staff can be treated. The crew also want the ship to be cleaned. The federal government, at the urging of the state government, has demanded that the ship leave.

The Premier of Western Australia, Mr Mark McGowan, expressed concern that allowing the ship to stay would attract other cruise liners to the state's ports.

"What I don't want to see is the Artania sit there and potentially attract ships from somewhere else," he told reporters.

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"If the ship needs to be cleaned, well, clean it and then get it on its way... It has to get back to Germany."

Across the Pacific, small island countries such as Vanuatu and the Cook Islands have been barring cruise ships from docking. The move has caused serious economic damage but was seen as crucial in a bid to keep the islands free of the coronavirus.

Mr McGowan last week proposed a solution that may prove more workable for larger countries. He suggested that authorities treat sick patients, allow foreign passengers to either stay aboard or go to an airport and fly home, and put locals in quarantine for 14 days. But the ship would then be required to leave and make its way through the open seas - a voyage that most crews currently seem unwilling to make.