Ousted Catalan leader Carles Puigdemont has travelled to Brussels, Spanish government officials said.
The development came after Spain’s state prosecutor announced it was seeking charges of rebellion, sedition and embezzlement for members of the ousted Catalan cabinet and the governing body of the regional parliament that allowed a vote to declare independence last week.
The crimes can be punished with up to 30, 15 and six years in prison respectively.
Chief prosecutor Jose Manuel Maza said he would ask judges for preventive measures against the officials, but did not specify if those would include immediate arrest and jailing while they await trial.
Belgian asylum state secretary Theo Francken said over the weekend that it would be "not unrealistic" for Mr Puigdemont to request asylum.