Immigration chief Benson Kwok says more than 12,000 people were denied entry to Hong Kong in the first five months of the year.

On an RTHK programme that aired on Sunday, Kwok said those refused permission to come into the city only amounted to 0.06 percent of the 20 million visitors during the period.

"There were a number of reasons, for example if we were suspicious about their reasons for coming to Hong Kong, like they could be here to work illegally and affect the job opportunities of locals," he said.

"There were also some visitors who didn't have proper travel documents. For example they didn't apply for a visa. Also, there were some we suspected had forged travel documents."

Asked about young people who left the SAR following unrest in 2019, Kwok said those who are patriotic and love Hong Kong are always welcome to return.

"Hong Kong people enjoy the freedom to enter or leave the SAR. So long as the person didn't violate the law, the Immigration Department will not stop him or her, nevermind asking the person questions," he said.

Kwok added that now more young people travel to the mainland in their free time, they have a better understanding of the importance of safeguarding national security.