"In order to safeguard water safety in the urban districts, the municipal government has decided to provisionally stop supplying water to the public water network," the government of Harbin city, provincial capital of China's northeastern Heilongjiang, said in a statement.

The order comes after a November 13 explosion at a petrochemical plant in Jilin city, about 380 kilometers (230 miles) up the Songhua river from Harbin.

The explosion killed at least five people and resulted in the temporary evacuation of tens of thousands of others who were forced to flee a cloud of toxic smoke.

"At present there is no sign of any abnormalities along the Songhua river in the Harbin section, but the environmental protection agency expects that up-river pollution could appear in the coming days," the government said.

Government officials, when contacted by phone, refused to say how many people would be affected by the water shortage, only saying that the water would be cut off for four days.

Harbin is a city of more than eight million people, but only some three million people live in the city's urban districts.

Locals aware of the pending water stoppage began hoarding water and food supplies on Sunday, amid government pronouncements to remain calm and "stop listening to rumors," state press reports said.

Local supermarkets reported all their bottled water had quickly sold out due to the panic buying.

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