MOS Food Service Inc. plans to double the number of its overseas outlets in five years to offset declining domestic sales.

The operator of the MOS Burger chain, Japan's second-biggest hamburger chain, plans to open about 230 restaurants overseas by 2013, adding to about 170 outlets it already operates in Taiwan, Singapore, Hong Kong and Thailand.

Japan's restaurant sales have slumped 15 percent over the past decade as the population ages and stagnant wages discourage people from dining out. MOS Food, which has about 1,400 restaurants in Japan, posted an 8 percent decline in first-quarter sales.

"We will be shifting the management resources to overseas as domestic sales have been struggling," President Atsushi Sakurada said in a recent interview.

South Korea, China, Malaysia, Indonesia and Australia are under consideration for the new stores, Sakurada said.

The company's net loss is forecast to widen to ¥600 million in the year ending March. The Tokyo-based company may return to profit next year as the performance of its Chinese noodle chain, Chirimentei, improves and new menus are introduced at MOS Burger, Sakurada said.