War-torn Yemen's healthcare system has "in effect collapsed" and coronavirus is spreading across the country, the United Nations has warned.
Jens Laerke, spokesman for the UN Office for the Co-ordination of Humanitarian Affairs (OCHA), described the situation as "extremely alarming".
He said people were being turned away from treatment centres partly because staff lacked protective equipment.
The Yemeni authorities have confirmed scores of infections, and 30 deaths.
But the UN says the real figures are almost certainly much higher.
The country's health system has been damaged by years of civil war and ventilators are in short supply.
Millions of Yemenis homeless; many are malnourished, and most of the population depends on aid.
What did the OCHA spokesman say?
Speaking at a briefing in Geneva, Mr Laerke warned that a lack of testing disguised the real infection numbers in Yemen.
"The actual incidence is almost certainly much higher. Tests remain in short supply. Aid agencies in Yemen are operating on the basis that community transmission is taking place across the country."
Mr Laerke said Yemen's economy was also suffering and efforts to combat the pandemic would fail without urgent help.
"If we do not get the money coming in, the programmes that are keeping people alive and are very much essential to fight back against Covid-19 will have to close.
"And then the world will have to witness what happens in a country without a functioning health system battling Covid-19. And I do not think the world wants to see that," Mr Laerke said.