Millions of schoolchildren in Vietnam returned to class on Monday after the country reported its 17th straight day of no domestically transmitted coronavirus infections.

The decision to reopen schools came after the Southeast Asian nation eased social distancing measures at the end of April -- with experts pointing to a decisive response involving mass quarantines and expansive contact tracing for its apparent success in containing the disease.

At a school in western Hanoi, secondary level students calmly lined up to have their temperatures checked before filing into classrooms for the first time in more than three months.

"I am very happy and excited because it's boring being at home," said 11-year-old Pham Anh Kiet.

"I feel safe when I wear a mask and have my temperature checked, I am not afraid of being infected with the virus," he added, before grabbing a classmate for a quick catch up.

Tran Dang Ngoc Anh, 12, said she'd missed her friends and teachers and was happy to be back -- despite being a little apprehensive about wearing "stuffy masks in classrooms".

There are around 22 million school-age children and university students across Vietnam. After being sent home in late January, some kids returned last week but others -- including primary school and kindergarten pupils -- will have to wait it out a further week.

Universities have begun opening one by one.

Vietnam has recorded just 271 virus cases and zero deaths, according to official tallies on Sunday. It has been more than two weeks since the country reported a domestically transmitted infection.

But far from letting their guard down, authorities are enforcing strict social distancing measures in schools -- with pupils ordered to stay 1.5 metres apart at all times. Everyone must wear masks.

Nguyen Xuan Khang, a headteacher in Hanoi, admitted it would be difficult to keep the little ones in line.

"When it's break time, the young ones... they are very active, it will be hard to help them maintain a distance," he said.

"But no problem, we have to accept that. All the parents give the kids masks, and we also bought 10,000 masks to give to the children. We have put a lot of hand sanitiser in the toilets."