[Updated at 7:40 a.m. ET] Chinese authorities have killed more than 20,000 birds from a live-poultry trading zone in Shanghai after an unusual strain of bird flu that has so far killed six people in the country was found in pigeons on sale in the city, state-run media Xinhua reported Friday.

Details of the slaughter of chickens, ducks, geese and pigeons come as the city prepares to temporarily close all its live poultry markets. It wasn't clear how long the market closures - announced Friday on the Shanghai Municipal Government's microblog account - would last.

[Posted at 1:27 a.m. ET] A sixth person in eastern China has died from an unusual strain of bird flu, Chinese health authorities said Friday.

A 64-year-old man died Thursday night in Huzhou, Zhejiang province, the provincial health bureau said Friday. He died hours after doctors had confirmed he had been infected with the H7N9 virus, it said.

The H7N9 strain of bird flu had not been detected in humans before the recent Chinese cases, which authorities began reporting on Sunday.