UN Secretary-General Antonio Guterres underscored the necessity of the World Health Organization (WHO) during the COVID-19 crisis in the face of a threat by US President Donald Trump to withhold funds for the UN agency.

"The WHO, with thousands of its staff, is on the front lines, supporting member states and their societies, especially the most vulnerable among them, with guidance, training, equipment and concrete life-saving services as they fight the virus," Guterres said in a statement on Wednesday, reported Xinhua news agency.

"It is my belief that the WHO must be supported, as it is absolutely critical to the world's efforts to win the war against COVID-19," he said.

Trump on Tuesday criticised the WHO's response to COVID-19 and threatened to freeze US funding for it.

Guterres said that once the current health crisis is over, there will be time to study how such a disease emerged and spread its devastation so quickly and to evaluate the performance of all involved.

But now is not that time. Now is the time for unity, for the international community to work together in solidarity to stop this virus and its shattering consequences, he said.

The situation on the ground seems to support Guterres' appeal for support for the WHO.

The confirmed number of COVID-19 cases in Africa has risen to more than 10,000 with more than 500 recorded deaths, according to the WHO.

While the virus was slow to reach the continent compared with other parts of the world, infections have grown exponentially in recent weeks and are continuing to spread, it warned.

Africa's first COVID-19 case was recorded in Egypt on February 14 and since then the number of African countries reporting cases has risen to 52 out of a total of 54.

The WHO said communities need to be empowered, and provincial and district levels of government need to ensure they have the resources and expertise to respond to the outbreaks locally.

The UN agency is working with governments across Africa to scale up their capacities in critical response areas such as coordination, surveillance, isolation, case management and contact tracing, infection prevention and control, risk communication and community engagement.

The chief spokesman for the secretary-general, Stephane Dujarric, said the United Nations is supporting the Nigerian government in efforts to curb the spread of the virus. Three ambulances were donated Wednesday to Lagos State, home to some 21 million people. Other essential preventive, testing and treatment equipment procured by the United Nations is expected to arrive in the country in the coming days.

In Zimbabwe, he said a severe climate- and recession-induced hunger is deepening the COVID-19 crisis. The World Food Programme said it is urgently calling for US $130 million through August to help millions of the most vulnerable people in the country.

A recent nationwide assessment found that the number of acutely food insecure Zimbabweans has risen to 4.3 million from 3.8 million at the end of last year, the spokesman said. More than half, 7.7 million people, of the country's population are regarded as food insecure.

In Venezuela, the UN Resident Coordinator and Humanitarian Coordinator for the country, Peter Grohmann, said the first shipment of 90 tons of UN life-saving supplies was scheduled to arrive on Wednesday to support the COVID-19 response.

The shipment includes 28,000 personal protective equipment kits for health workers on the front line as well as oxygen concentrators, pediatric beds, water quality control products and hygiene kits.

The supplies have been financed by the international donor community, the UN Central Emergency Response Fund and UN agencies, Dujarric said.

The UN Children's Fund (UNICEF) in Spain has delivered the first batch of medical supplies to health authorities to support the fight against the pandemic, he said.

The shipment includes hand sanitizer and gloves and more supplies are expected in the coming days, including face masks, gloves, detection kits, and personal protective equipment.

UNICEF Executive Director Henrietta Fore said COVID-19 is generating an unprecedented global economic crisis, with the economic destruction cruelly and unequally distributed.

For the world's poorest countries, the financial fallout caused by the pandemic, combined with debilitating debt-service obligations, are hampering their ability to prevent further transmission and protect citizens, she said in a statement on Tuesday. "The situation is already dire, and it is only going to get worse."

A report of the International Labour Organization said the COVID-19 pandemic is expected to wipe out 6.7 percent of working hours globally in the second quarter of 2020, equivalent to 195 million full-time workers.

The UN Economic and Social Commission for Asia and the Pacific reports in a study that COVID-19 is having far-reaching economic and social consequences for the region, with strong cross-border spillover effects through trade, tourism and financial linkages.

It highlights the immediate risk to the region's economic outlook posed by the pandemic, already deepening an economic slowdown.