A growing number of mainlanders are trying to exploit a loophole by travelling to Hong Kong without permits and pretending to be in transit.
The Immigration Department said yesterday that 1,632 travellers had been refused entry for this reason in the first three months of this year, more than half the total of 2,940 for all of last year.
Mainlanders who arrive as transit visitors are required to leave for a stated overseas destination before returning to the mainland.
But immigration officers say many only pretend to be in transit because they cannot be bothered returning to their registered places of residence to obtain or renew Hong Kong entry permits or have been duped by travel agents who say they can get away with it provided they have a ticket to somewhere else.
"They either find it more convenient to use their passports to travel to Hong Kong without taking the trouble to return to where their hukou is," Fung Pak-ho, assistant director of the Immigration Department in charge of enforcement and removal assessment, said yesterday.
"Or they are persuaded by travel agencies that paying several hundred dollars to buy a flight ticket can fool immigration into believing they are transit visitors."
In the past two days alone 23 were arrested in a crackdown, codenamed Breakshadow, that began on Tuesday at border checkpoints including the airport.
Four were charged with making a false representation to an immigration officer and three were convicted and sentenced to two months' jail.
State broadcaster CCTV earlier reported that some unscrupulous travel agencies in Shenzhen and Zhuhai had helped mainlanders get counterfeit visas or air tickets to travel with Chinese passports to Hong Kong, exploiting the seven-day permit-free period for mainlanders in transit.
Some travel agencies would cancel flight bookings once their clients had successfully entered Hong Kong.
Fung warned mainland visitors not to make any false representations to an immigration officer as the maximum penalty for such an offence was a fine of HK$150,000 and 14 years' jail.
About 29,000 mainlanders were declined entry to Hong Kong last year.