Security Secretary Chris Tang on Tuesday warned that prison inmates are using treats such as chocolates to recruit followers and "build up forces" to endanger national security.
Tang said these prisoners, whom he didn't name, are either on remand because of alleged national security offences or are serving time for their involvement in the social unrest of 2019.
The security minister claimed that inmates are making use of visitors with religious or district council backgrounds to "spread their messages" to the outside world.
He also said the authorities have noticed that some organisations, including the 612 Humanitarian Relief Fund, have been sending out letters asking prisoners to "continue with their struggle."
"These [actions] seriously affect the rehabilitation programme and have sown seeds of endangering national security," Tang told reporters at Legco.
He went on to say that there are prisoners who recruit "followers" by giving them treats.
"In conjunction with all those issues, what they achieve is they will establish a special group of people who have privileges. Where do the privileges come from? They come from extra resources, items," he said.
"And through these influences, they try to disseminate their sense of [being] against the [SAR] and central governments. And through these, they will endanger national security and the security of Hong Kong."
Tang said some inmates have abused the complaints mechanism in a bid to deter prison officers from doing their jobs, but he stressed that staff won't give in and will stay professional.