A view of the Victoria Harbor in Hong Kong, July 22, 2016. [Photo/IC]

In Hong Kong, Beijing and Shanghai, it now takes more than 30 years for an average household to buy a 90-square-meter apartment, making them among the top five cities with most unaffordable housing.

The ranking, compiled by advisory firm Oxford Economics, is based on price-to-income ratios across the world.

Hong Kong tops the list, followed by Mumbai. London, on fifth spot, is the highest ranked non-Asian city.

The home price in Beijing averaged 40,178 yuan ($5,820) per square meter, according to statistics released by the Municipal Commission of Housing and Urban-Rural Development earlier this month.

Beijing and Shanghai's red-hot market comes as the nation's real estate sector suffers rollercoaster cycles, in part fueled by the government's policy shift.

Since October, dozens of Chinese cities have announced measures, including purchase limits and tightened mortgage restrictions, to prevent prices surging out of control.

However, rental yield in Mumbai, Shanghai and Beijing is "remarkably low," noted the report, adding that this could be an indicator that valuations in those cities are "stretched."