Transport workers in Barcelona are staging the first of four days of strikes, increasing road traffic problems in the northeastern Spanish city as the four-day Mobile World Congress gets underway.

The city's TMB transport company urged people not to use the underground system during the strike by subway employees Monday and Wednesday. The company's bus workers will strike Tuesday and Thursday.

A minimum service of 50 percent has been promised for rush hour periods.

The strikes have been called to demand wage increases.

Mobile World Congress organizers said they would provide hotel shuttle buses to help the tens of thousands of visitors get to the fair, which started Monday on the outskirt of the city.