Meanwhile, Iran, the hardest-hit country in the Middle East, urged the United States to remove sanctions as the total number of confirmed COVID-19 cases in the Islamic republic edged toward 20,000 on Friday.

Iranian President Hassan Rouhani asked the American people to press Washington to lift sanctions against Tehran, according to Iran's presidential website.

"US sanctions have targeted major sectors of Iran's financial and economic system, which has inflicted hundreds of billions of dollars of loss to Iran's economy and people," said Rouhani.

In a rare relief to people worrying about the epidemic, the pace of daily new infections in South Korea has shown marked signs of slowing since earlier this month, according to a report by the Yonhap news agency.

But the authorities are still on high alert over new clusters of infections, including at a call center in Seoul's Guro district and nursing hospitals in Daegu and surrounding North Gyeongsang Province.

In the thick of the world's fight against the pandemic, the WHO called on people to remain hopeful and cited the case of Wuhan in China.

Wuhan, a city that has borne the brunt of the COVID-19 outbreak in China, provides hope for the rest of the world that even the most severe situation of COVID-19 can be turned around, said Tedros.

Calling it a "success", he noted Wuhan, capital of central China's Hubei Province, reported no new cases for the first time since the epidemic outbreak started.

According to the Health Commission of Hubei province, no new infections or suspected cases of the novel coronavirus were reported on Thursday in Wuhan, marking two days in a row of zero reports at the epicenter of the epidemic in a months-long battle with the deadly virus.

"The experience of cities and countries that have pushed back this virus give hope and courage to the rest of the world," Tedros said at a daily briefing.