Police on Friday said they had arrested another four people on suspicion of conspiracy to defraud after they allegedly received vaccine pass exemption certificates from doctors who allegedly handed out such documents without holding medical consultations.

Six doctors were earlier arrested over the suspected scams and one of them has been charged. A seventh doctor is wanted by the police.

The latest arrests involve four women, aged between 25 and 48, who are believed to be civil servants.

A total of 26 alleged recipients of exemption certificates allegedly provided by the doctors have now been arrested.

The government said last week that it would stop recognising certificates issued by the seven doctors.

A legal challenge against that move has now been filed. Kwok Cheuk-kin, known as the "king of judicial reviews", argues that annulling the certificates is a violation of the International Bill of Human Rights.