Sales of fast food giant KFC in China slumped an estimated 36 percent last month, according to parent Yum! Brands, as consumers shunned chicken due to the H7N9 bird flu outbreak in humans.

For Yum overall, which includes other restaurant chains such as Pizza Hut, Chinese same-store sales -- a measure of turnover in established outlets -- fell an estimated 29 percent in April, according to an exchange filing on Friday.

An outbreak of H7N9 avian influenza, found in humans for the first time, has killed 35 people in China since the government began reporting figures in late March, according to the National Health and Family Planning Commission.

The ministry said Monday that four new deaths had occurred in the past week.

Chinese cities have shut live poultry markets in response to the outbreak.

"Beginning the first week of April, publicity surrounding avian flu in China has had a significant, negative impact on KFC sales," Yum said.

China is a key market for Yum, which has more than 4,200 KFC restaurants in the country.

"Historically, the impact of this publicity has initially been dramatic at KFC but relatively short-lived," Yum said. "As in the past, we are reminding consumers that properly cooked chicken is perfectly safe to eat."

But Yum recorded a 20 percent year-on-year fall in its China sales in the first quarter, according to a previous statement, after authorities found excessive levels of antibiotics in chicken KFC sourced from local suppliers.

KFC said it had taken measures to ensure food safety and win back trust from customers.

China has seen several food safety scares in recent years, including one in which the industrial chemical melamine was found in dairy products in 2008, killing at least six babies and making 300,000 ill.