Chief executive Carrie Lam stood before a group of senior officials at a closed-door ceremony for the pledge, which all the finance hub's 180,000 civil servants will be expected to make in the coming weeks.

Those taking the oath promise to uphold Hong Kong's mini-constitution and "bear allegiance" to the city and its government.

A government spokesperson said the oath-taking would "strengthen the public's confidence in political-appointed officials".

Civil servants were one of the groups that took to the streets in large numbers last year calling for greater democracy and police accountability.

Tens of thousands joined one rally that was expressly organised by civil servants -- some of whom posted anonymised ID cards online as a way to signal their support for the movement -- a move that infuriated Beijing.