Africa must "wake up" to the coronavirus threat and prepare for the worst, the head of the World Health Organization (WHO) has said.

The continent should learn from how the spread of the virus has sped up elsewhere, Tedros Adhanom Ghebreyesus said.

He warned that while Africa's confirmed cases were currently low - around 640 - there was no reason for complacency.

"Africa should wake up, my continent should wake up," said the Ethiopian, the WHO's first African head.

Health experts warn that strained public health systems in Africa could become quickly overwhelmed if the virus takes hold.

"WHO's recommendation is actually mass gatherings should be avoided and we should do all we can to cut it from the bud, expecting that the worst could happen," Mr Tedros told a news conference in Geneva, where the WHO is based.

In Africa, 16 people have died from Covid-19, the respiratory illness caused by coronavirus: six in Egypt, six in Algeria, two in Morocco, one in Sudan and one in Burkina Faso.

In South Africa, which has 116 cases, President Cyril Ramaphosa has declared a state of disaster, restricting travel, closing schools, banning mass gatherings and ordering bars to close or limit numbers to 50.

Other countries on the continent have also been imposing similar restrictions this week.

From Saturday, Nigeria says it will stop arrivals from any country where there are more than 1,000 cases of coronavirus.