"The detention of Navalny is another attempt to intimidate the democratic opposition in Russia. A swift and unequivocal response at the EU level is essential. Respect for citizens' rights is the cornerstone of democracy," Morawiecki wrote on Twitter.

"I appeal to the authorities in Russia to release the detainee immediately," he wrote. In September, Morawiecki suggested that Russia was a "hostile regime", after Germany said Navalny had been poisoned with a Soviet-style Novichok nerve agent.