Chinese citizens registering for new mobile-phone services will now have to scan their faces to verify their identities, a move that will further increase the government’s scrutiny of its people.

The requirement, which came into effect Sunday, is aimed at minimizing telephone fraud and preventing the reselling and illegal transfer of mobile phone cards, the Ministry of Industry and Information Technology said in a notice in September. In the past, Chinese citizens applying for a new mobile phone number had to personally present...