Slovakia's prosecutor general said on Tuesday he had ordered the release of 12 Greenpeace activists who had been held "unlawfully" for staging a protest at the EU country's largest and oldest brown coal mine.

The campaigners from Belgium, Czech Republic, Finland, Germany and Slovakia were detained without bail last week after hoisting a banner saying "End coal age!" on the tower of a lignite mine in Novaky, central Slovakia.

Their detention and bail rejection sparked a protest in the capital Bratislava on Monday and criticism from Slovakia's top politicians including the president and prime minister.

Greenpeace had also called for their immediate release. "Today, I issued an order to release all 12 people," Slovakia's prosecutor general Jaromir Ciznar told local media on Tuesday, adding that "these people are detained unlawfully". He added that the district court, which had ordered their detention without bail on Sunday, had "improperly" defined their actions.

Slovakia's liberal President Andrej Kiska said in a statement Monday that he did not "understand how we can push activists into the role of criminals".

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