Hong Kong is seeking the help of mainland authorities to stem an influx of asylum seekers, mainly from South Asia, who are increasingly turning to people smugglers, or 'snakeheads', to bring them over the border.
But a human rights advocate in the city said refugees should not be stopped from seeking asylum.
Immigration Department assistant director Eric Chan Kwok-ki said asylum seekers were increasingly seeking entry to Hong Kong via the mainland. They paid snakeheads to smuggle them to the city by boat.
Mr Chan said most of those caught were men from Sri Lanka and Pakistan. Those countries' citizens lost visa-free access to Hong Kong because many asylum seekers were found to be coming to Hong Kong simply to earn money.
Mr Chan said of the more than 500 people claiming to have been tortured whose cases the department was handling, more than 120 people had admitted they entered Hong Kong illegally.
The department will ask mainland police and Hong Kong's marine police to step up patrols for snakehead boats.
'We're trying to tackle the problem at source,' he said.