HANOI (REUTERS) - Vietnam's capital, Hanoi, extended Covid-19 restrictions on Monday (Sept 6) for a further two weeks, as the authorities launched a plan to conduct tests on the city's eight million people to try to curb a climb in infections that started in late April.

The South-east Asian country dealt successfully with the virus for much of the pandemic, but the virulent Delta variant has proved more challenging in recent months.

Covid-19 has infected more than 536,000 people in Vietnam and killed 13,385, the vast majority in the past few months.

Hanoi, which has ordered people to stay home and halted all non-essential activities since July, has divided the city into "red", "orange" and "green" zones based on infection risk.

"People in quarantine camps, isolated areas or in red areas will be tested three times per week," city authorities said in a statement late on Monday, adding that people in other zones would be tested every five to seven days by either a polymerase chain reaction or rapid antigen test.

Barricades on Monday separated red zones from other areas, photographs posted on social media and media outlets showed.

Hanoi has been reporting 50 cases daily on average and has recorded over 4,100 cases since the pandemic began, official data showed.

Hanoi authorities are eager to keep the outbreak from reaching the intensity seen in Ho Chi Minh City, which accounts for nearly half of the total infections and 80 per cent of fatalities.

In the southern business hub, where a strict lockdown is in place until Sept 15, people have been encouraged to test themselves using antigen Covid-19 kits after health services were overwhelmed.

In a rare live broadcast of questions from the public to an official late on Monday, Mr Phan Van Mai, chairman of Ho Chi Minh City, said some restaurants in safe zones would be allowed to reopen for takeaway and that city authorities would look to gradually reopen the economy.

One-third of Hanoi's residents have received at least one dose of a vaccine and the Health Ministry on Sunday called on the capital and Ho Chi Minh City to vaccinate all adult residents with at least one dose by Sept 15.

Vietnam has one of the lowest coronavirus vaccination rates in the region, with only 3.4 per cent of its 98 million people fully vaccinated, and 19 per cent with one shot.