The Foreign Office said in an updated travel advisory on Tuesday that it advises against "all but essential" travel to mainland China.
Raab said the government now advises British citizens in China "to leave the country if they can, to minimize their risk of exposure to the virus.''
The Foreign Office said it is continuing to work to evacuate British citizens from the epicenter of the virus outbreak, Hubei province.
Singapore has reported six more cases of the new virus, raising its number of confirmed infections to 24. The health ministry said four cases involved human-to-human transmission and the other two were Singaporeans who were evacuated from Wuhan, the Chinese city at the center of the outbreak. It said there is no evidence of widespread sustained community contagion in Singapore.
It said two of the Singaporean women worked in a health product shop patronized by Chinese tourists, while another woman was a tour guide who brought tour groups to the shop. The fourth woman was the Indonesian maid of one of the Singaporean women working in the health shop.
The ministry said the tour guide and the two women working at the shop had prolonged interaction with Chinese travelers, including at least two from Guangxi who were confirmed to have the virus. It said the tour guide showed no symptoms when she went to the National Center for Infectious Disease on Monday but tests confirmed Tuesday she has the virus.
Similarly, it said the two Singaporeans who returned from Wuhan showed no symptoms when they tested positive Monday.
It said all Singaporeans returning from Wuhan have been tested for the virus.
Hong Kong has reported two new local cases of the virus, bringing its total infection to 17.
Chuang Shuk-kwan, who heads the communicable disease branch at the Center for Health Protection, says the two have no travel history to mainland China and are believed to have contracted the virus locally. This brings locally transmitted cases in the city to four, with no clear source of infection.
Chuang says it "indicates significant risk of community transmission" and could portend a "large-scale" outbreak. One of the new cases is a 64-year-old woman who works in a boutique while the other is a 60-year-old retired man.
She says the man had seen four private doctors before he was hospitalized and tested positive for the virus. Doctors initially didn't think he had the virus as his symptoms were mild and similar to seasonal influenza, she said.
Hong Kong's leader, Carrie Lam, shut on Monday all but two land and sea border crossings with the mainland into the semi-autonomous territory to try to stem the spread of the virus.
Authorities in Indonesia's tourist island of Bali have rejected East Timor's request to quarantine its 17 citizens due to be evacuated from Wuhan following the deadly virus outbreak in China.
Ketut Suarjaya, who heads Bali's Health Provincial Office, says an official response was sent to East Timor's government on Tuesday through the Indonesian embassy in Dili.
Bali Vice Gov. Tjokorda Oka Artha Ardhana Sukawati told reporters earlier that East Timor's government had asked for Indonesia's assistance in quarantining its 17 nationals, all students, in Bali for up to three weeks when they land on the resort island.
Sukawati says that "tourism stockholders in Bali did not agree because we would maintain Bali as a safe place for tourism."
Indonesia's Foreign Minister Retno Marsudi said Sunday that the government would temporarily suspend all flights to and from the Chinese mainland as of Wednesday.
She also said the country has officially suspended the visa-free and on-arrival visa policy for all Chinese citizens after the outbreak of the coronavirus. The ban also applies to foreign nationals who have traveled to China in the past 14 days.
The government decision to quarantine Indonesian nationals evacuated from Wuhan on a remote Natuna island has sparked anger among residents. Hundreds of people burned tires during weekend protests near the naval base where some 238 evacuees were brought Sunday and are being isolated for 14 days.
Japan Airlines says it is canceling some flights to and from China and reducing seats on other flights because of a virus outbreak that has led to a sharp decline in travel demand and growing global travel restrictions.
JAL says in a statement that flights to China will be reduced from 98 to 43 flights per week between Feb. 17 and March 28, and some flights prior to Feb. 16 may also be affected.
The flights connect Tokyo with Beijing and Shanghai, as well as other cities such as Guangzhou, Dalian and Tianjin.
Separately, All Nippon Airways said Tuesday that it will temporarily decrease or suspend flights to and from Chinese cities.
ANA says that the seven roundtrip flights a week connecting Narita and Beijing will be canceled from Feb. 10 through March 29
The 14 weekly round-trip flights connecting Haneda and Beijing will be reduced to seven a week over the same period.
Cambodia's leader said Wednesday he will visit Wuhan, the Chinese city at the center of a new virus outbreak, to meet with students from his country studying there.
Prime Minister Hun Sen said on his Facebook page that he would fly Wednesday to Wuhan from South Korea's capital, Seoul.
He initially said Chinese authorities had agreed to the trip but later updated his posting to say he was awaiting permission.
There are no commercial flights currently operating from Seoul to Wuhan, and Hun Sen didn't explain how he would get there. He is in Seoul for a conference organized by a private group.
Hun Sen said he plans to give moral support to the students in Wuhan and tell them not to fear the virus. A number of other countries have evacuated their citizens from the city.
He told Cambodians in a television broadcast last week that the virus does not threaten them, and he would not ban flights from China.
The virus has sickened more than 20,600 people worldwide, most of them in China. More than 420 have died.
Belgium has reported its first case of a new virus in a person who was repatriated from the Chinese epicenter of the outbreak.
The health ministry said Tuesday the person was in good health and does not show any symptoms of the disease. The individual was among nine Belgians repatriated from Wuhan, China, over the weekend.
The infected person was taken to a special hospital for further care while the other returnees remain under observation.
More than 180 cases of the new type of coronavirus have been confirmed beyond mainland China, which has more than 20,000 cases.
The Singapore Airshow will proceed next week despite the withdrawal of South Korea's air force team and 16 exhibitors because of a new virus.
Experia Events said Tuesday an aviation conference that is part of the airshow will be cancelled as the would-be participants instead focus on handling the outbreak.
Experia said 10 exhibitors from China and six exhibitors from other countries couldn't participate in the Feb. 11-16 event due to Singapore's ban on all Chinese visitors and company bans on employee travel.
Experia said temperature screenings and other measures will be used at the exhibition center and a medical team will be on standby.
The new type of coronavirus has infected more than 20,000 people, mostly in China. Several Asian countries have reported cases, including Singapore, which has 18.
More than 100 Malaysians have been quarantined after being evacuated from the Chinese city at the center of a viral outbreak.
An AirAsia plane carrying 107 Malaysians and their non-Malaysians spouses and children from Wuhan landed at the Kuala Lumpur airport early Tuesday.
They immediately underwent medical screenings, and the National Disaster Management Agency said two people who didn't pass the screenings were immediately taken to the hospital.
Its statement said the others were sent to a surveillance center in southern Negeri Sembilan state to be quarantined for 14 days.
Malaysia has recorded eight cases of the new type of coronavirus, all involving Chinese travelers.
The leader of semi-autonomous Macao is asking the city's casinos shut for two seeks after a worker at one of them tested positive for the new virus sweeping China.
Ho Iat Seng made the request on Tuesday as the total number of cases in mainland China surged past 20,000. Macao's more than two dozen casinos account for about half of the local economy and are hugely popular with Chinese visitors, generating more than four times the revenue of those in Las Vegas. Macao has so far recorded 10 cases of the virus.
Ho told reporters he would meet with heads of the casinos to discuss details. Public transport and other services were also being cut back to the minimum needed to deal with emergencies, Ho said. He urged residents to stay home and leave only to buy necessities such as food.
With more than 20,000 cases reported, China has begun moving patients suffering from a new virus into rapidly built or adapted facilities, although the degree of medical isolation among them appears to vary widely.
The first 50 patients were moved Tuesday into Huoshenshan Hospital, a prefabricated structure on the outskirts of the city of Wuhan, the epicenter of the outbreak. Earlier footage appeared to show the 1,000-bed facility equipped with state-of-the-art medical equipment, including negative-pressure isolation wards to prevent the virus from breaking the air seal. A second hospital, Leishenshan, is due to be ready soon and will add another 1,600 beds.
Elsewhere in Wuhan, authorities are converting a gymnasium, exhibition hall and cultural center into hospitals with a total of 3,400 beds to treat patients with mild symptoms of the virus. Television footage of those facilities showed beds placed in tight rows in large rooms without dividers between them.
Japanese health officials are conducting extensive medical checks on all 3,700 passengers and crew of a cruise ship that returned to the country after one passenger tested positive for the new coronavirus.
Japanese officials say a number of people on board are ill, though no one else has yet tested positive for the fast-spreading virus that emerged in China last December.
The U.S.-operated Diamond Princess returned to a port in Yokohama, near Tokyo, late Monday, ending a 14-day tour during which it stopped at Hong Kong and several other Asian ports before returning to Japan.
Japanese government and tour company officials say they were notified by Hong Kong that an 80-year-old male passenger who got off the boat on the island tested positive for the virus.
The ship's captain said Monday night that Hong Kong's health authorities notified the ship about the passenger's infection on Saturday, according to a recording of the announcement tweeted by a passenger. According to the announcement, the patient is recovering.