In a statement released on Tuesday, the bloc threatened to "take measures on those responsible for the observed violence, unjustified arrests, and falsification of election results" in Belarus.
Speaking on behalf of the 27 member states, the EU's foreign policy chief, Josep Borrell, said in the statement that state authorities in Belarus “deployed disproportionate and unacceptable violence causing at least one death and many injuries."
He added: "Thousands of people were detained and the crackdown on freedoms of assembly, media and expression intensified."
The statement also called on the Belarusian authorities "to release immediately and unconditionally all detained.”
Earlier, the foreign ministers of Poland, Lithuania and Ukraine called on the authorities in Belarus to refrain from using force amid protests in that country as the opposition accused Lukashenko of rigging his re-election victory.
Official results handed Lukashenko, in power for more than a quarter of a century, an 80 percent share of the vote in Sunday's election, while Svetlana Tikhanouskaya, Lukashenko's main electoral opponent, took around 10 percent, the Reuters news agency reported.
Polish Prime Minister Mateusz Morawiecki has called for a special summit of EU leaders to focus on Belarus.
Source: PAP, Reuters, consilium.europa.eu
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