Yum Brands Inc. estimated same-store sales in China fell about 13 percent in the third quarter as a result of a food safety scare in July when a former supplier was said to have improperly handled meat and used expired food.

The company's shares fell 4.3 percent at $68.40 in trading after the bell on Wednesday.

"Since July 21st, Yum Brands' China division has experienced a significant, negative impact to sales at both KFC and Pizza Hut following adverse publicity regarding improper food handling practices by former supplier, Shanghai Husi," the company said in a filing.

"While sales are beginning to rebound, they continue to be negative."

The food safety scare in China was triggered by a TV report showing improper meat handling by a supplier, Shanghai Husi Food, a division of U.S. meat supplier OSI Group LLC.

Yum plans to "vigorously" pursue legal action against OSI and Husi to recover damages from the incident, the company said.