Japan has "serious concerns" about the situation in Myanmar and urges the release of detained leader Aung San Suu Kyi, Foreign Minister Toshimitsu Motegi said Monday.

In a statement issued after Myanmar's military staged a coup, Motegi said Japan strongly urges it to "promptly restore a democratic political system" in the Southeast Asian country.

The Japanese government has strongly supported Myanmar's democratization process and opposes moves against this, the foreign minister said.

Japan's top government spokesman Katsunobu Kato said, "It is important that the relevant parties resolve the situation peacefully through dialogue."

Kato, the chief Cabinet secretary, told a press conference Japan was gathering information via its embassy in Yangon, Myanmar's largest city, and will ensure the safety of its citizens.

Myanmar's military seized power and declared a nationwide state of emergency on Monday, local and other media reported, with a spokesman for the ruling National League for Democracy saying Suu Kyi, President Win Myint and other senior party officials had been detained.

The coup followed a landslide victory by the NLD in the November general election, the results of which the military has disputed as fraudulent.

Japanese firms in Myanmar have also been scrambling to gather information on the situation. There are around 400 firms with business in the country, according to the government-backed Japan External Trade Organization.

Toyota Motor Corp., which plans to commence operations of its first production plant in the country this month, said it is currently "assessing" the situation. The sentiments were echoed by Suzuki Motor Corp., which owns two plants in Myanmar and plans to open another in September.

Aeon Co. said that it has confirmed the safety of Japanese staff posted in the country, and will keep its supermarkets open while prioritizing the safety of local workers.

The major Japanese retailer operates supermarkets in a joint venture with a local company. Although it has managed to make contact with the joint venture, it is "unable to get information in real time," a spokesperson said.

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