Image caption Officials have ordered the cull of 20,000 birds

Chinese officials in the city of Shanghai have ordered the temporary closure of its poultry markets due to the H7N9 bird flu outbreak.

A spokesman for the city authorities said the decision was taken on grounds of public safety.

The city has already begun a mass slaughter of poultry after the virus was discovered in pigeons at a market.

Six people have died in this latest outbreak. The H7N9 virus is a form of avian flu not seen before in humans.

China has officially confirmed 14 cases and six deaths due to H7N9 infection as of Friday, the World Health Organization (WHO) said in a statement.

The cases are reportedly from eastern China, including in Shanghai and Zhejiang province.

WHO says there is currently no evidence of human-to-human transmission.

"We have 14 cases in a large geographical area, we have no sign of any epidemiological linkage between the confirmed cases and we have no sign of sustained human-to-human transmission," WHO spokesman Gregory Hartl said in Geneva.

The latest fatality was a farmer, 64, who died in Zhejiang province, state-run media say.

Four of the bird flu fatalities and six of the 14 cases have been recorded in Shanghai.

The city is also monitoring another person who was in close contact with one of those who died after showing flu-like symptoms.

Shanghai health official, Wu Fan, was quoted by Agence-France Presse news agency as saying that the person tested negative for H7N9.

"There is no possibility of spreading the infection overseas," Wu Fan also told a press conference.

Officials ordered the slaughter of at least 20,000 birds starting late on Thursday after the virus was detected in pigeons sold in Huhuai market.

The market was sealed and police stood watch as workers disinfected the areas, reports say.

Xu Wei, a spokesman for the Shanghai government, said trading of live poultry will be suspended on Saturday.