An American expert on North Korea says a growing number of people in the impoverished state rely on informal markets to make up for shortages of food and other necessities.

Stephen Linton, chairman of the Eugene Bell Foundation, told an audience in Washington Tuesday that the communist government turns a blind eye to many practices that are inconsistent with Pyongyang's state-controlled economy.

He said people from various socioeconomic groups, including farmers, factory workers and government officials, increasingly benefit from these unauthorized markets. These markets, he said, thrive especially along the border with China, North Korea's closest ally.

Linton said the North Korean government is reluctant to make a radical change to its state-controlled economy. But it tolerates the spread of a market economy on an informal basis, because such gaps in the system are helping it stay in power.

Linton, who has made many humanitarian visits to North Korea, says he has not seen any unrest there, despite chronic food and other shortages.

The Eugene Bell Foundation provides medical and other assistance to rural North Korea.

South Korea's Yonhap news agency quotes Park In-ho, managing editor at the DailyNK, a Seoul-based Internet news outlet, as saying Pyongyang cannot stop the expansion of a market economy so it is letting market activities proceed within a controllable boundary.