A professor of engineering said on Friday that stricter penalties may ensure Covid patients instructed to isolate at home make proper use of new electronic wristbands, though he stressed that trust was also vital for the system to work.

Authorities began distributing the wristbands on Friday to ensure that infected people don't flout isolation requirements and go out, increasing the risk of infection.

William Wong, a Chinese University academic who was involved in the distribution of similar wristbands to inbound travellers two years ago, told RTHK's Hong Kong Today programme that some elderly people and those who had inadequate WiFi at home had experienced difficulty using the devices.

"The whole operation depends a lot on trust," he told RTHK's Samantha Butler. "Some of these people are not really trustworthy; they are not actually following the requirements and then they walk out and that was causing the trouble.

"I think what they're trying to do now is to make it stricter. If you are caught you will probably be heavily fined," he added.

"And then some of the people, they do not know how to operate the thing, so we'll have to help them to start the device. So I think one of the problems is ability, because there are many elderly people around. There are also people in households where they do not have enough WiFi facilities around."

Health Secretary Lo Chung-mau said last week that authorities are also looking into turning the QR codes of infected patients red on their LeaveHomeSafe app as a further safeguard against non-compliance.

The health chief stressed that such a measure would make it easier to identify people who are infected.