July 1 (Reuters) - Myanmar arrested four executives of supermarket chains, including an official of a Japanese joint venture, for selling rice at inflated prices, state media said on Monday, as the war-torn country's ruling junta struggles to stabilise its economy.

The impoverished Southeast Asian country has been in turmoil since its military deposed an elected civilian government in February 2021, sparking widespread protests that have morphed into an nationwide armed resistance.

Authorities said they arrested 11 people, including rice traders and officials of mills and retailers, accusing them of inflating prices by 31% to 70% from prescribed levels, the Global New Light of Myanmar newspaper said.

In Tokyo, Japan's chief cabinet secretary, Yoshimasa Hayashi, said police in Myanmar's commercial capital of Yangon were questioning a Japanese national.

"The Japanese government intends to continue taking appropriate steps while urging local authorities for his early release," he told reporters.

Such efforts include maintaining contact with the Japanese citizen's employer and offering necessary support, he added.

The junta-run Myanmar newspaper said an executive from supermarket chain Aeon Orange, a joint venture between Japan's Aeon Co and Yangon-based Creation Myanmar, was among those arrested.

A junta spokesman did not respond to a telephone call to seek comment.

An Aeon spokesperson told Reuters that a company employee had been detained in Myanmar, and it was working with the Japanese embassy to get more details.

The owner of a rice mill in Myanmar said many businesses in the sector were struggling because of a mismatch between the official foreign exchange rate and black market rates governing most transactions, such as buying imported fuel and fertiliser.

"It is a loss for us to sell the rice at the government's standard rate," he said, speaking on condition of anonymity as the issue is a sensitive one.

"Myanmar still has plenty of rice. This situation has happened because the government wants to restrict the price."

For years, black market rates for Myanmar's kyat currency have been significantly higher than the central bank's reference rate of 2,100 to the dollar.

The currency hit a record black market low of about 4,500 to the dollar in late May, and has since stayed broadly around that level, three foreign exchange traders said.

Amid escalating violence, poverty in Myanmar is more widespread than at any time in the last six years and labour shortages and a depreciating currency have made it harder to do business, the World Bank has said.

Last month, the junta arrested 35 people, cracking down on gold and foreign exchange traders and agents selling foreign real estate, in a bid to prop up the fast-depreciating currency. (Reporting by Reuters staff and Kiyoshi Takenaka and Rocky Swift in TOKYO; Writing by Poppy McPherson and Devjyot Ghoshal; Editing by Michael Perry and Clarence Fernandez)