The World Health Organisation on Thursday said it was working alongside authorities in Yemen to stop the spread of Covid-19 to the country.
Yemen has no confirmed cases of the virus but the internationally recognised government has halted flights and urged travellers to quarantine themselves.
Government officials have also ordered schools to close.
All border crossings will be closed except for commercial and humanitarian shipments, the state-run Saba news agency reported.
“There are no cases of Covid-19 in Yemen, although testing is extremely limited," said Altaf Musani, the WHO representative for Yemen.
"We are working with our partners all over the world to bring capability to the country."
More than 4,500 people have been screened in the past 30 days across the country, Mr Musani said.
“In the past 24 hours, more than 3,000 people who have entered Yemen have been asked to be screened and some are put in quarantine,” he said.
The WHO is working with authorities to introduce measures, Mr Musani said.
The government has been identifying points of entry for those arriving by air, land and sea, the WHO said.
Rapid response teams have been stationed around the country.
Yemen's shattered healthcare infrastructure and already weakened population suggest the virus could wreak more chaos if it reached there.
The health system is working at 50 per cent capacity and the coronavirus would “greatly overstretch it”, the organisation warned.
Yemen’s five-year conflict has killed more than 100,000 and unleashed a humanitarian crisis.
Nearly 80 per cent of the population live off humanitarian aid while millions are on the brink of starvation, leaving them highly vulnerable to the disease.