Users of about 12 million pre-paid and service plan SIM cards have registered under their real names, the government says, adding that people can complete the registration even beyond Thursday's deadline.

Director-general of communications Chaucer Leung told an RTHK programme on Tuesday that the registration progress has been satisfactory, with publicity and support services in place.

All pre-paid SIM cards must be real-name registered before Thursday, otherwise they will be deactivated from that day.

"If people have not registered after the deadline, as long as the [pre-paid] SIM card is still valid with remaining balance, they can still ask their telecom service provider for a resubmission of registration," Leung said.

Leung also said the administration is aware of people online offering to complete the real-name registration on behalf of others.

He said authorities have passed the information they collected to the police for investigation, warning that such acts amount to a criminal offence.