The Immigration Department on Wednesday said more than 900,000 Hong Kong SAR passports have expired without being renewed since 2020, as it called on people to renew them soon.

An assistant director of the department, Fan Hiu-sing, said with many countries relaxing their entry rules, people planning to go on a trip should pay attention to the validity period of their passport, noting that many countries require incoming travellers to have a passport valid for six months or more.

"Compared to pre-Covid times, the number of people who haven't renewed their expired passport has roughly doubled. We believe it's because people haven't had the chance to travel during the pandemic," he said.

"We'd like to appeal to the people to renew their passport if expired, because there may be swarms of applications later on and their trip may be affected."

Fan said two vehicles will be touring the city until early September with staff on board who can help people apply for or renew their passport.

People can submit their application and have their photo taken at the mobile service stations.