The growing number of imported coronavirus cases in China risked fanning a second wave of infections at a time when "domestic transmission has basically been stopped", a spokesman for the National Health Commission said.
"China already has an accumulated total of 693 cases entering from overseas, which means the possibility of a new round of infections remains relatively big," the spokesman, said.
In the last seven days, China has reported 313 imported cases of coronavirus but only six confirmed cases of domestic transmission, the commission's data showed.
There were 45 new coronavirus cases reported in the mainland for yesterday, down from 54 on the previous day, with all but one involving travellers from overseas.
Most of those imported cases have involved Chinese returning home from abroad.
Airlines have been ordered to sharply cut international flights from today. And restrictions on foreigners entering the country went into effect yesterday.
Five more people died yesterday, all of them in Wuhan, the industrial central city where the epidemic began in December.
But Wuhan, the capital of Hubei province, has reported only one new case on the last 10 days.
A total of 3,300 people have now died in mainland China, with a reported 81,439 infections.
Around 80% of cases of Covid-19 will be a mild to moderate illness, close to 14% have severe disease and around 6% are critical.
Generally, you need to be 15 minutes or more in the vicinity of an infected person, within 1-2 metres, to be considered at-risk or a close contact.
Yesterday marked the fourth consecutive day that Hubei province recorded no new confirmed cases. The sole case of domestically transmitted coronavirus was recorded in Henan province, bordering Hubei.
All airports in Hubei resumed some domestic flights today, with the exception of Wuhan's Tianhe airport, which will open to domestic flights on 8 April. Flights from Hubei to Beijing remain suspended.
In Europe, the death toll from coronavirus passed 20,000 with Italy and Spain each reporting more than 800 dead in one day, as US President Donald Trump decided against putting the hard-hit New York region under quarantine.
Up to one-third of the world's population is under lockdown with millions of jobs lost and healthcare systems under severe strain.
Globally, the death toll has soared past 30,000 and officials in some countries say the worst still lies ahead.
Mr Trump decided late last night against imposing a broad lockdown on New York and its neighbours after a strong push back from local political leaders and warnings of the panic it could spark.
"A quarantine will not be necessary," he tweeted, about eight hours after he stunned the New York metropolitan region - the epicentre of the US outbreak - with a proposal to place it under quarantine.
On the recommendation of the White House CoronaVirus Task Force, and upon consultation with the Governor's of New York, New Jersey and Connecticut, I have asked the @CDCgov to issue a strong Travel Advisory, to be administered by the Governors, in consultation with the....— Donald J. Trump (@realDonaldTrump) March 29, 2020
The Centers for Disease Control and Prevention, however, asked residents not to travel except for essential purposes.
Mr Trump's reversal came on the same day the US death toll topped 2,100, more than doubling in just three days. Of the fatalities, more than a quarter were in New York City.
Health officials say they fear New York may follow the deadly path charted by Italy, with health professionals exhausted and hospitals desperately short of protective equipment and ventilators.
The United States now has the highest number of confirmed COVID-19 infections globally with more than 124,000 cases, according to a tally from Johns Hopkins University.
One of the fatalities announced yesterday was that of a Chicago infant who was younger than one year old, marking an extremely rare case of juvenile death in the global pandemic.
More than 664,000 cases of the novel coronavirus have been officially recorded around the world since the outbreak began late last year, according to the Johns Hopkins tracker.
Variations in testing regimes - and delays in providing sufficient tests in some countries - mean the true number is likely far higher.
In Italy, a cardiologist from Rome who has recovered from Covid-19 recalled his hellish experience.
"The oxygen therapy is painful, looking for the radial artery is difficult. Desperate other patients were crying out, 'Enough, enough'," he told AFP.
Infection rates in Italy are on a downward trend. The head of the national health institute Silvio Brusaferro predicted a peak "in the next few days".