MADRID (AP) — Hundreds of taxis are holding up traffic in Madrid and Barcelona as drivers continue their protests to demand tighter regulations companies using ride-hailing apps.

Drivers in the Spanish capital began an open-ended strike at dawn on Monday. Their leaders said after meeting with city officials that talks to end the dispute were unsuccessful and the protest would continue.

In Barcelona, taxis have demonstrated outside the Catalan regional parliament building and gathered at a downtown traffic circle, snarling traffic.

Spanish taxi drivers complain that rival ride-hailing app drivers compete unfairly since they don't have the same regulations and costs.

Police are on standby after previous taxi demonstrations led to violence against vehicles using the internet-driven ride-hailing platforms like Uber.