WHO chief Dr Tedros Adhanom Ghebreyesus said the number of cases outside China had increased 13-fold over the past two weeks.

He said he was "deeply concerned" by "alarming levels of inaction" over the virus.

A pandemic is a disease that is spreading in multiple countries around the world at the same time.

However, Dr Tedros said that calling the outbreak a pandemic did not mean the WHO was changing its advice about what countries should do.

He called on governments to change the course of the outbreak by taking "urgent and aggressive action".

"Several countries have demonstrated that this virus can be suppressed and controlled," he said.

"The challenge for many countries who are now dealing with large clusters or community transmission is not whether they can do the same - it's whether they will."

Governments had to "strike a fine balance between protecting health, minimising disruption and respecting human rights".

"We're in this together to do the right things with calm and protect the citizens of the world. It's doable," he said.

Earlier, Germany's Chancellor Angela Merkel warned that up to 70% of the country's population - some 58 million people - could contract the coronavirus.

She said since there was no known cure, the focus would fall on slowing the spread of the virus. "It's about winning time," she said.

Some German virologists dispute the high figure. Former federal government adviser on disease control, Prof Alexander Kekulé, told German media he saw a worst case scenario of 40,000 cases.

 to Iran but there was still a shortage of ventilators and oxygen.

"Iran and Italy are suffering now but I guarantee you other countries will be in that situation very soon," he said.

What else is happening?

In the western US, Washington state is banning some large gatherings in certain areas and has told all school districts to prepare for possible closures in the coming days. The governor of Seattle's King County said he expected a serious coronavirus outbreak within weeks.

In the eastern US, New York's governor announced that troops would be sent into New Rochelle, in an attempt to contain an outbreak of the virus, as the total number of US cases passed 1,000 on Wednesday.

A one-mile (1.6km) containment zone was in force around the town north of Manhattan. Some individuals have been quarantined.

A number of countries have imposed sweeping travel restrictions. India has suspended most visas for foreigners until 15 April. Guatemala is banning European citizens from entering from Thursday.

Several countries - including Sweden and Bulgaria, as well as the Republic of Ireland - have recorded their first deaths, while the number of confirmed cases in Qatar jumped from 24 to 262.

China - where the virus was first detected - has seen a total of 80,754 confirmed cases and 3,136 deaths. But it recorded its lowest number of new infections, just 19, on Tuesday.

According to worldometers.info, hosted by the American Library Association,  the infectious disease has spread to  more than 121 countries and territories and infected more than 124,000  people. More than 4, 580 people have died, while there have been about 67, 050 cases of recovery.