Fast food restaurants operator Yum Brands Inc's sales at established outlets fell well short of Wall Street estimates on Wednesday, as fewer diners visited Pizza Hut and KFC than expected.

Worldwide sales at Yum's restaurants open for at least a year rose 1 per cent in the three months ended March 31, while analysts had expected a 2 per cent increase, according to Thomson Reuters I/B/E/S.

Same-store sales at KFC and Pizza Hut also missed expectations.

The results come as U.S. fast food chains including Yum Brands and McDonald's Corp are competing fiercely for customers' loyalty with dollar menus, discounts and new breakfast items.

Yum said total revenue fell 3 per cent to $1.37 billion but topped estimates of $1.09 billion, thanks to stronger sales at Taco Bell.

Yum's net income rose to $433 million or $1.27 per share in the first quarter, from $280 million or 77 cents per share a year earlier.

Excluding one-time items, Yum earned 90 cents per share.

Yum's shares fell about 1 per cent in premarket trading on Wednesday.