OAKLAND, United States — The first passengers were taken ashore from a coronavirus-hit cruise ship after it docked Monday at California's port of Oakland, in what officials called an "unprecedented and difficult" operation involving thousands on board.

The Grand Princess arrived shortly after noon (3 a.m. Tuesday in Manila) in the San Francisco Bay after days stranded at sea with more than 3,500 passengers and crew.

Emergency workers equipped with gowns, gloves, respirators and face shields loaded those requiring immediate treatment into ambulances, while all port employees and residents were cleared from the fenced-off landing site.

More than 900 Californian residents will disembark next from the ship, in a stage of the operation expected to take most of the day.

"Individuals will be led off the ship in smaller groups," and "anyone who is symptomatic... will be fitted with a surgical mask and disembarked via a separate gangway" to avoid disease spread, said a statement from Governor Gavin Newsom's office.

The ship, which has 21 confirmed novel coronavirus infections, had been idling off the San Francisco coast since Wednesday.

• Some Pinoys catch COVID-19 on ship stuck off San Francisco: cruise operator

Passengers gathered on balconies were "whooping and waving at dock workers onshore" as the ship drew into port, said Carolyn Wright, 63, of New Mexico, from on board the vessel.

Tents were set up on the Oakland quayside, with the surrounding floor doused in what appeared to be disinfectant, she added.

Buses and flights were lined up to transport passengers.

After initial screening, those who don't require acute care will be quarantined for 14 days at US military bases in California, Texas and Georgia -- or flown to their home countries, in the case of foreign residents.

Those at US bases will be given private single rooms with access to private bathrooms, said Pentagon spokesman Jonathan Hoffman.

Passengers will be fully tested at their onward destination to avoid delays.

Crew will remain on board and the ship will leave San Francisco Bay, the company said.

The entire site will be decontaminated by pressure-washing with a bleach solution once the operation is complete.

- Dancing on deck -

Wright earlier Monday said the mood had been lifted on board by the prospect of finally reaching land, and guests were briefly allowed to leave their cabins.

Some couples danced on deck as others walked laps around the huge ship.

"It really feels wonderful to have gotten out and stretched our legs," Wright told AFP. "I feel kind of energized and happy. It just makes you feel like, OK, things are happening and things are now moving."

She added: "Hopefully things will be smooth from here on."

Newsom said Sunday the whole operation to bring passengers ashore was expected to be a "2-3 day process," but warned it could take longer.

"We are still working out the enormity of complexity of making sure we prepare the site and... prepare for a quick turnaround," he said.

On Monday, Princess Cruises announced full refunds, scrapped on board charges and offered free future cruises to affected passengers on the Grand Princess.

But Canada -- which had 240 citizens on the ship -- became the latest country to warn people to avoid taking cruises, after the US issued a similar warning to vulnerable Americans Sunday.

© Agence France-Presse