At least 10 people on a cruise ship moored off the coast of Yokohama have tested positive for the new coronavirus, Japan's Health Minister said yesterday.

They are among 31 people whose test results have come in, out of 273 who have been screened so far, Mr Katsunobu Kato told a news conference. There were 3,711 people on the Diamond Princess liner, comprising 2,666 passengers and 1,045 crew from 56 countries and regions.

The 10 people who tested positive for the coronavirus, which originated in the central Chinese city of Wuhan, consist of nine passengers - three Japanese, three Chinese, two Australians and one American - and a Filipino crew member.

The remaining people on board will be kept under quarantine for 14 days.

Prime Minister Shinzo Abe told Parliament they "will not be allowed to come ashore for the time being" as a precautionary measure, adding: "Checking the health of the passengers and crew is our priority, while we will also do all possible to prevent any spread of the infection."

The 3,600 passengers and crew of another cruise ship, the World Dream, which docked in Hong Kong yesterday, were also barred from leaving.

Health officials boarded the ship, which is owned by Dream Cruises and operated by Genting Hong Kong, to conduct checks for the coronavirus, media reported.

Three mainland Chinese travellers, who had been on board from Jan 19 to 24, tested positive for the virus. About 30 crew members have reported symptoms of cough and fever, and the ship was denied entry into Taiwan's Kaoshiung port on Tuesday. Most of those on board are from Hong Kong.

Dream Cruises said that none of the passengers on the current cruise is a Chinese passport holder.

The cases exemplify fears of how the confined spaces of a cruise ship - where passengers intermingle in common areas - could well catalyse the spread of a virus.

The Hong Kong government announced further border restrictions yesterday, including the closure of two cruise terminals.

In a previous case in Italy, 6,000 people were briefly isolated on board their vessel until two suspected cases of the new coronavirus tested negative.

The lockdown of the Diamond Princess comes after a former passenger, an 80-year-old man from Hong Kong, tested positive for the virus after he disembarked.

He went to Shenzhen briefly on Jan 10 and returned to Hong Kong, where he took a flight to Tokyo on Jan 17. He then boarded the cruise ship at Yokohama on Jan 20, which docked in Kagoshima in southwestern Japan en route to Hong Kong, where he alighted on Jan 25.

The Diamond Princess returned to Yokohama on Monday via the ports of Chan May and Halong Bay in Vietnam, Keelung in Taiwan and Naha in Okinawa.

Japanese health officials are testing people on board with symptoms such as fever or cough, as well as those who have been in close contact with sick patients.

All passengers are confined in their cabins, with meals delivered to them by crew members in protective gowns. The ship would go farther out to sea briefly for marine operations such as freshwater production, before returning near Yokohama for more food and provisions.

There are now 35 confirmed cases in Japan, including the 10 patients from the ship.