"It represents another step towards the dismantling of the rule of law and a further blatant violation of human rights in Myanmar and yet another major setback for democracy in Myanmar since the military coup on 1 February 2021," an EU spokesperson said in a statement.

Suu Kyi has been in military custody since last year's coup ousted her government and plunged Myanmar into turmoil.

She was handed the sentence Wednesday for alleged corruption as part of a barrage of criminal cases that could see her jailed for decades.

The EU said the proceedings were "a clear attempt to exclude democratically elected leaders, including Aung San Suu Kyi" from a dialogue process called for by the ASEAN regional bloc.

"We reiterate our urgent call for the immediate and unconditional release of all political prisoners as well as all those arbitrarily detained since the coup," the EU statement said.

The German foreign ministry also condemned the sentencing as "politically motivated" and "another step to dismantle the rule of law".

"The military junta must end its repression against the people of #Myanmar, release all political prisoners and put an end to the violence," the ministry wrote on Twitter.

The 27-nation bloc has already imposed sanctions on the Myanmar junta and its key economic sources over the coup and subsequent crackdown.