A group of union members set fire to tires in La Línea de la Concepción (Cádiz) on Thursday, close to the border with Gibraltar. The protest, which saw access to the British territory closed off for around half an hour, was prompted by the failure of the local authorities to pay municipal workers their salaries.

Around 50 union members have been holding daily protests since last week, and have decided to step them up given the council's failure to honor payments.

"We've been protesting every day, but we have had to come and burn tires and cut off the access to Gibraltar, like we did last week, because there is no other way to get them to listen," José Porras, of the UGT union in Cádiz, told news agency EFE.

The municipal workforce is 850-people strong. They have not received their salaries since the end of April.