Japan called Monday for Myanmar's military to release Aung San Suu Kyi and restore democracy, saying it was opposed to moves that pushed the country "backwards".
"We request the release of stakeholders including state counsellor Aung San Suu Kyi who was detained today," Japan's foreign ministry said in a statement, urging the army "to quickly restore the democratic political system in Myanmar".
The ministry said Japan had been "strongly supporting the democratic process in Myanmar" and was opposed to "moves going backwards."
In Tokyo, several hundred protesters -- mostly from Myanmar -- demonstrated outside the United Nations University calling for the international community to intervene to secure Suu Kyi's release following Monday's coup.
Japan has long had warm ties with Myanmar, offering considerable aid and private investment.
Japan's foreign direct investment in Myanmar stood at $768 million in 2019/20, and several prominent Japanese firms operate in the country.
Tokyo has pressed Suu Kyi to tackle ethnic discrimination and violence, but humanitarian groups have also called on Japan to take a more assertive role.
Suu Kyi last visited Japan in 2019, while Japanese officials have made several high profile trips to Myanmar in recent years.