Police on Thursday said they had arrested 23 people over dozens of phone scam cases where the victims reportedly lost HK$5.6 million between them.

Officers said the cases involved 42 victims in total, with one person losing HK$1.36 million to a caller claiming to be a mainland police officer.

Authorities believe a syndicate was behind the cases.

Officers also said there has been a growing trend of people's personal details being stolen and used in scams after the real-name registration of SIM cards took effect.

"Two [of those arrested] may have had their identity cards details stolen. They might have disclosed the information to fraudsters when applying for jobs online, and the fraudsters then used their identity cards to register new phone numbers online," inspector Kwok Ka-shing said.

Kwok said other people were arrested on suspicion of collecting cash from the victims, or having lent their bank accounts to the alleged scammers for money laundering.