Police on Wednesday said that a man had been arrested on suspicion of scamming people by sending phishing text messages that start with a hashtag.

A little more than a year ago, authorities introduced a scheme under which registered firms and organisations can send messages that start with the symbol, in a bid to combat scams.

The force said officers received around 30 reports in the past week about suspected fraud messages with the hashtag.

Officers then arrested the suspect, 23, on Monday, and plan to lay charges against him.

"After careful planning, officers arrested the man in Mong Kok on suspicion of conspiracy to defraud," said senior inspector Wan Chun-hong from the police's Cyber Security and Technology Crime Bureau.

"The suspect was inside a van, and police seized two mobile phones and a radio jammer that was in operation."

Wan said at a police briefing that one victim claimed to have lost around HK$22,000 after clicking a hyperlink from a suspicious text message and giving out credit card information.

The Office of the Communications Authority said they found that some of the recent suspicious hashtag messages were not sent out by local telecommunication firms.

Principal regulatory affairs manager Andrew Lo said people should be extra careful when they see their phone signal dip suddenly from maximum coverage to 2G, as messages they receive during that period could be from people using illicit radio jammers.

"The jammers would pretend to be a 2G base station, because under this standard, mobile phones generally won't authenticate the 2G station," he said at the same briefing.

"So it's possible to deceive these phones, connect to their network and send fraudulent messages to them."

Lo added that extra caution is also needed when the messages involve strange hyperlinks, or that they ask for money.