The warning came as the first European died from the new COVID-19 strain, which first emerged in December in central China but has now spread to over 25 countries and caused over a dozen deaths outside the country.
In total, there are 2,360 confirmed dead and almost 78,000 infected.
A 78-year old Italian from the Veneto region died in the hospital after testing positive for the virus.
Italy has locked down ten towns and asked over 50,000 people to stay home amid a flurry of cases in the area - a move with echoes of China’s lockdown of entire cities in Hubei province at the centre of the outbreak.
In China, the number of cases outside Hubei, where millions remain under effective quarantine, has been generally declining, although new hotspots were found in several prisons and hospitals yesterday (Feb 21).
But just 31 new cases were reported outside the central province Saturday, as the national number of cases rose past 76,000.
Concerns have also risen about the reliability of the official data, however, after Hubei officials changed methods of counting cases and amended their figures again.
A WHO-led team of experts are set to visit Wuhan, the capital of the province, today.
Meanwhile, WHO chief Tedros Adhanom Ghebreyesus warned that the “window of opportunity” to contain the international spread of the outbreak was “narrowing”, as cases surged across the Middle East and in South Korea.
He warned that if countries did not quickly mobilise to fight the spread of the virus, “this outbreak could go in any direction. It could even be messy.”
Cases of the deadly virus were reported in a range of countries in the Middle East yesterday, including the first cases in Israel and Lebanon.
Iran said four people there had died and 18 been infected from the outbreak.
Nearly 350 people have been infected in South Korea, including two deaths, making it the hardest-hit country outside China.
The US advised citizens to avoid travelling by cruise liner in Asia because it said the vessels acted as amplifiers of the virus.
Several Australians and an Israeli evacuated earlier this week from the stricken Diamond Princess cruise ship tested positive for coronavirus on returning to their home countries.
They were previously cleared in Japan.
The cases will fuel questions about Tokyo’s policy of allowing former passengers to return home after testing negative.
Two former passengers, both Japanese and in their 80s, died in Japan on Thursday (Feb 20).
The British government confirmed on Twitter that an evacuation flight had left Japan today with 32 British and European passengers on board, as well as British government and medical staff.
Tokyo 2020 Olympic organisers today postponed training for their army of volunteers due to the coronavirus outbreak, but said that there was “no consideration” of cancelling the Games.
‘Grim and complex’
Nearly 400 new cases were reported nationwide in China today, less than half the number of new cases the previous day.
The drop in new cases of the novel coronavirus came as officials in Hubei province were ordered to revise figures to clear “doubt” around the data.
Officials retroactively revised upwards previously reported data for two days in the last week - the latest in a string of amendments to the figures officially reported at the epicentre.
Several changes in Hubei’s counting method has further complicated efforts to track the spread of the illness.
China has said the slowing cases are evidence that its drastic containment measures are working - but fresh infections emerged at two Beijing hospitals, and more than 500 others were reported in prisons across the country.
At a Politburo meeting chaired by Chinese President Xi Jinping yesterday, the leadership said the epidemic’s peak “has not yet arrived”, and the situation in Hubei and Wuhan remains “grim and complex,” according to state media.
Many nations have banned travellers from China and airlines have suspended flights to and from the country.