Immigration staff turned away an average of 72 would-be mainland visitors a day in the first three months of this year - half as many again as a year ago, before solo travellers were allowed to visit the city.
Most of the 6,443 travellers were rejected because officers believed their documents were forged or because they doubted the reasons they gave for visiting Hong Kong, an Immigration Department spokesman said.
In the first three months of last year, 4,272 mainland visitors were refused entry.
The spokesman attributed the surge in rejections partly to the department's increased efforts to stop mainlanders seeking illegal employment or engaging in prostitution during their stay. Of those refused entry in the first quarter of this year, 2,057 held business visas - 63 per cent more than a year ago.
Guangdong authorities said 358 of the 1.6 million visitors under the solo travel scheme launched last July had committed crimes in Hong Kong, including 165 for overstaying and 72 for prostitution.
Mo Lian, of the Guangdong Public Security Department's division of exit and entry administration, said suspicious applications for the scheme would be vetted thoroughly, such as those who made multiple applications to visit Hong Kong but who did not appear to have the money to pay for a trip.