Major cruise lines are cancelling their sailings from Singapore or pulling out of Asia entirely for the remainder of the season, putting the brakes on one of the region's fastest-growing tourism sectors.

Some cancellations have come within the last several days, as more ports in the region shut their doors to cruise ships amid fears over the spread of the coronavirus.

Celebrity Cruises told The Straits Times yesterday that it will be moving its Celebrity Millennium cruise ship to the United States three months earlier than planned.

"Up until today we had not intended to cancel the remaining season in Asia. However, due to continual and unpredictable changes in travel restrictions and port closures, we feel this is the best decision for the health and safety of all," a spokesman said.

Its Celebrity Constellation voyages on March 2 and 17, originally scheduled to disembark and embark in Singapore, will now make a round trip from Dubai instead.

Royal Caribbean said two sailings on Quantum of the Seas, due to depart Singapore tomorrow and on Feb 24, have been cancelled in the light of "current regional travel conditions". "The Singapore market remains of great importance to us and we look forward to returning there very soon," a spokesman said.

The flurry of cancellations comes after a cruise ship which left Hong Kong on Feb 1 was turned away from Japan, Guam, the Philippines, Taiwan and Thailand, despite assurances by operator Holland America that there were no infected passengers on board.

After nearly two weeks at sea, the MS Westerdam, carrying more than 2,000 passengers and crew members, received permission to dock at the Cambodian port of Sihanoukville yesterday morning. A spokesman said no Singaporeans were on board.

Ports in Hong Kong and South Korea have also suspended entry for cruise ships despite heightened screening and sanitation measures put in place by operators.

Travellers who had booked a regional cruise on the Sapphire Princess, due to depart from Marina Bay Cruise Centre yesterday, were given short notice of its cancellation.

Quality assurance inspector Matt Strine, who arrived in Singapore from the United States on Sunday, said: "We found out less than 24 hours before we were to depart that it was cancelled via e-mail... We were really looking forward to it."

He will instead spend two nights on Sentosa before returning home, said Mr Strine, 43, who is on his first visit to Singapore. "It's a beautiful city. If not for the cruise problem, this would have been the vacation of a lifetime," he said.

The Diamond Princess remains under quarantine off the coast of Japan, with more than 200 passengers now confirmed to have the virus.

Norwegian Cruise Line said it has cancelled all Asian itineraries for the Norwegian Spirit from April 15 to Dec 7.

A 24-day voyage departing from Cape Town, South Africa, on March 22 will also now end in Greece instead of Singapore, with an extra three days added to the itinerary.

At least one cruise operator has added Singapore to the list of countries where recent visitors will require additional screening to board its vessels. This comes after the Republic, the country with the highest number of confirmed cases outside China, raised its disease outbreak response to orange last Friday.

British-American cruise line Cunard has also said the Queen Mary 2 will skip a scheduled stop in Singapore this month.

Ms Annie Chang, director of cruise at the Singapore Tourism Board (STB), said Singapore's cruise terminals remain open, though arriving ships must meet Singapore's entry requirements.

While it is too early to determine the full impact of the virus outbreak, Singapore is in a good position to recover, given the sector's strong growth and a diverse range of cruise brands and markets, she said.

The growth potential for cruises in Asia remains bright, said Ms Chang, with the number of cruise passengers sailing in South-east Asia expected to grow to reach an estimated 4.5 million by 2035.

Singapore, positioned as an Asian cruise hub, "remains well-poised to capture that, due to our geographical location and good infrastructure", she said.

The STB on Tuesday projected a 25 per cent to 30 per cent drop in visitor arrivals this year as the global spread of the coronavirus continues to batter the tourism sector.