A homeless woman lay dead at a Hong Kong McDonald's restaurant for hours surrounded by diners who failed to notice her, sparking concern over the city's "McRefugees".

The woman, who police say was between 50 and 60, was found dead Saturday morning and has been held up as an example of the growing number of homeless people who seek shelter in 24-hour restaurants.

"Officers arrived upon a report from a female customer (that a person was found to have fainted)," police said in a statement.

"The subject was certified dead at the scene."

Local media said the woman was slumped at a table, 24 hours after she first entered the restaurant in the working class district of Ping Shek.

She had not moved for seven hours before fellow diners noticed something was wrong, according to Apple Daily, citing CCTV footage.

The woman was thought to have regularly spent nights in the McDonald's, the South China Morning Post said.

The city's Social Welfare Department said it was "highly concerned" about the incident.

"We endeavour to support street sleepers to enhance their self-reliance... the subject is a complex social problem," a department spokeswoman said.

There are concerns over the plight of the homeless population in the affluent southern Chinese financial hub, although the number of homeless is relatively low, estimated at more than 1,000 by local NGOs.

Many are forced to live on the street as they cannot afford to rent even the tiniest home as housing prices are sky high.

In sweltering temperatures and high humidity, some find shelter in air-conditioned restaurants that are open around the clock.

"McDonald's Hong Kong would like to express our grief over the unfortunate incident at our Ping Shek Estate restaurant," Wendy Lam, senior director of McDonald's Hong Kong, said.

"We welcome everyone to visit our restaurants any time. In order to provide a pleasant dining environment, we would not disturb our customers, but our service will be offered promptly upon request," she added.