Union representatives were due to meet officials of Prime Minister Pedro Sanchez's government later in the day to try to resolve the dispute, in which taxi drivers have choked main roads and snarled airports, bus and train stations since Saturday.

Along with counterparts in many other European countries, Spain's taxi drivers say that ride-hailing apps have made it impossible to compete.

"Uber and Cabify are putting the viability of the taxi sector and 130,000 jobs at risk...The union considers this unfair competition intolerable," the UGT union said in a statement.

Union representatives say the current law of one ride-hailing licence for every 30 taxi licences is not being respected and want an end to the practise of transferring ride-hailing permits between drivers.