A Spanish judge on Oct. 16 ordered that two leaders of Catalan separatist groups be put in prison without bail while they are investigated for possible sedition, media outlets reported.

Jordi Sanchez, leader of the Catalan National Assembly and Jordi Cuixart, who heads the Omnium Cultural association, are being investigated for their alleged involvement in the Oct. 1 referendum, which the Spanish government considers illegal, The Independent reported.

The chief of the Catalan police, Josep Lluis Trapero, was also questioned but was later released without bail, although his passport was confiscated, The Independent said.

Responding to the court's decision, Catalan leader Carles Puigdemont said on Twitter: "Spain jails Catalonia's civil society leaders for organizing peaceful demonstrations. Sadly, we have political prisoners again," in an indirect reference to the military dictatorship under Francisco Franco, Reuters reported.

Puigdemont in an Oct. 10 speech said the region had voted to secede from Spain but will delay putting independence into effect while it seeks dialogue with the Spanish government.

The Catalan National Assembly plans to hold demonstrations against their leader's incarceration in Barcelona on Oct. 17.