Europe is now the "epicentre" of the coronavirus infection, the World Health Organization (WHO) has warned, saying it was impossible to know when the outbreak would peak.

"Europe has now become the epicentre of the pandemic," WHO chief Tedros Adhanom Ghebreyesus said in a virtual press conference on Friday.

Excluding China, the continent now had more reported cases and deaths than the rest of the world combined, he said.

"More cases are now being reported every day than were reported in China at the height of its epidemic."

The virus, which first surfaced in China in December, has now killed more than 5,000 people, "a tragic milestone", according to Tedros.

Cases worldwide have topped 132,000, according to WHO, which is the health agency of the United Nations. About 68,000 victims have recovered, according to Johns Hopkins University.

Maria Van Kerkhove, who heads the WHO's emerging diseases unit, said it was not possible to predict how the pandemic will develop.

"It's impossible for us to say when this will peak globally. We hope that it is sooner rather than later."

Their comments came as countries across the world tried to limit the infection's spread, tightening borders, closing schools and cancelling events.

Tedros said such measures could help, but stressed that countries needed to take "a comprehensive approach.

"Not testing alone. Not contact tracing alone. Not quarantine alone. Not social distancing alone. Do it all," he said.

He stressed the need to do more to detect, protect and treat cases.

"You can't fight a virus if you don't know where it is," he said, calling on countries to "find, isolate, test and treat every case, to break the chains of transmission."

"Every case we find and treat limits the expansion of the disease," he said. "Do not just let this fire burn.

"Any country that looks at the experience of other countries with large epidemics and thinks 'that won't happen to us' is making a deadly mistake."

Michael Ryan, who heads the WHO's emergencies programme, stressed that so-called social distancing measures, including banning public gatherings and school closures, "are not a panacea".

"They are not going to stop this" on their own, he said.

Borders tightened

Travel to the US from most of Europe was suspended for 30 days beginning Friday, a move that has led to anger and confusion among some in the continent.

Turkey will from Saturday suspend flights to Germany, France, Spain, Norway, Denmark, Belgium, Austria, Sweden and the Netherlands until April 17.

The Czech government will ban foreign travellers from entering and Czechs from leaving from March 16.

Several European countries and airlines have limited travel to and from Italy, the continental centre of the pandemic.

The number of people who have died after catching the virus has risen to 1,266 in Italy, the worst-hit country after China.

Italy recently imposed a weeks-long national lockdown after previous attempts to quarantine affected areas to limit the infection's spread failed.

Meanwhile on Friday, Spain, which has the most coronavirus cases on the continent after Italy, joined a growing list of European countries to declare a state of emergency over the health crisis.