China's largest metropolis has completed building a vast bunker in case of explosions, emissions of poisonous gas or nuclear radiation, news report said Sunday.

The complex covers 90,000 square meters and can accomodate 200,000 people, according to the Shanghai Morning Post.

The underground haven has 15 passages nearly 2.5 miles (4km) in length that link to office towers and residential apartments. It is also connected to the subway system, enabling people to flee from one district to another.

Water, power and ventilation systems can support the bunker's population for between seven and fifteen days. In times of peace, some parts can be used as garages, warehouses or commercial facilities, the report said.

The article did not mention the exact location of the bunker.