Several North Korean restaurants in Northeast China's Liaoning Province said on Thursday they had stopped serving South Korean clients, triggering speculations it was caused by the recent defections of North Korean employees.

"It's an order from the [North Korean] government that all the restaurants in Shenyang and across the country should stop serving clients from South Korea," a waitress at the Peony Restaurant in Shenyang, Liaoning's capital, told the Global Times on Thursday.

"The ushers had stopped many South Koreans, almost every day, and those clients just left without complaining," said she.

She added that the ban is likely to continue without disclosing the reason.

A waitress at the Pyongyang Restaurant, another popular North Korean restaurant in Shenyang, also confirmed the ban.

A receptionist at the Pyongyang Koryo restaurant in Dandong, a Liaoning border city, told the Global Times that they have never received South Korean clients, adding they receive many  Chinese and North Korean customers.

Japan's Yomiuri Shimbun newspaper reported on Thursday that among some 100 North Korean restaurants in China, those in Beijing and Dandong took the lead in suspending service to South Koreans since June.

However, several restaurants in Beijing told the Global Times that they continue to serve South Korean clients, adding that they have never heard of such an order.

They can dine and enjoy the performances, though our clients are mostly Chinese, said a waitress at the Pyong Yang Urban restaurant in Beijing.

Another waitress at the Hae Dang Hwa restaurant in Beijing told the Global Times on Thursday that they receive South Korea clients every day, and that it's impossible to deny service to them.

South Korea's Unification Ministry said 13 North Koreans who worked at a restaurant run by North Korea at a third country were seeking political asylum in South Korea, Reuters reported in April.