The city has screened over 88,000 people returning from Da Nang since July 8, performing rapid tests on over 70,000, Nguyen Khac Hien, director of the Department of Health, said on Monday.

But the rapid test kits ran out on Monday afternoon, leaving around 18,000 unable to be tested, he said.

Hien said: "The number of people screened exceeded our expectations. We recommend that people should monitor their own health, and if one has symptoms like coughing, fever or breathing difficulty, they must go to medical facilities."

The Covid-19 rapid test kits analyze blood droplets to determine if a person is infected with the novel coronavirus. They typically produce results within 10 minutes.

If a rapid test is positive, the person has to take a standard Covid-19 test in which a throat swab sample undergoes a real-time polymerase chain reaction (RT-PCR) test. If the RT-PCR test is negative, the suspected case is deemed not to have contracted the novel coronavirus.

Hanoi had around 100,000 rapid Covid-19 test kits and used 20,000 of them earlier this year, chairman of the city People’s Committee, Nguyen Duc Chung, said.

Since late July, when the first local infection was found there after over three months, Da Nang has become the epicenter with 142 cases, many linked to some local hospitals like the Da Nang Hospital and the Da Nang Hospital C.

Hanoi has reported two non-imported cases: a 23-year-old man in Nam Tu Liem diagnosed on July 29 and a 76-year-old man in Tay Ho found infected a day later. Both visited Da Nang in July.

Vietnam has had 652 Covid-19 cases, 271 of them active, 374 having recovered and seven dead.

The seventh death, that of a 62-year-old woman in Da Nang, occurred early on Tuesday morning.