European Union chiefs on Monday denounced the coup by Myanmar's military and demanded the release of civilian leaders detained in the crackdown.

"I strongly condemn the coup in Myanmar and call on the military to release all who have been unlawfully detained in raids across the country," tweeted European Council President Charles Michel.

"The outcome of the elections has to be respected and democratic process needs to be restored," he said.

European Commission President Ursula von der Leyen echoed the condemnation and insisted on Twitter that "the legitimate civilian government must be restored".

The bloc's foreign policy chief Josep Borrell wrote that the "Myanmar people want democracy".

"The EU stands with them," he said.

He demanded in a statement that "President Win Myint, State Counsellor Aung San Suu Kyi, and all others who have been arrested must be immediately and unconditionally released".

Borrell said the moves by the military "bring back painful memories of previous decades".

"We are in touch with our international partners on this most pressing issue to ensure a coordinated response," the statement said.

Myanmar's military seized power in a bloodless coup on Monday, detaining democratically elected leader Suu Kyi as it imposed a one-year state of emergency.

The military has justified its power grab by alleging fraud in the November elections that Suu Kyi's National League for Democracy (NLD) party won in a landslide.

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