The tenors fell silent at Barcelona's opera house on Friday where a performance of Turandot was cancelled as a general strike and mass protests brought Catalonia to a halt after Spain's top court jailed nine separatist leaders.

On the fifth day of a massive mobilisation against Monday's Supreme Court judgement, the operatic shutdown was a symbol for how the protests are impacting daily life in the region, and its economy.

As 14,000 striking students marched to the city centre, traffic was halted on at least seven regional highways and nine other major roads.

Spanish carmaker Seat stopped production at its factory near Barcelona, which employs 6,500 people, and Barcelona's most visited monument, the Sagrada Familia basilica, closed its doors after protesters massed outside.

And along the Paseo de Gracia, luxury boutiques were shuttered, the nearby patches of blackened tarmac a testimony to four days of running battles between police and protesters.

Alarm bells

In this wealthy northeastern region which accounts for around a fifth of Spain's GDP, the ongoing protests, the violence and Friday's general strike have generated a flurry of warnings from business organisations.

And with at least six countries issuing travel warnings for visitors heading to Barcelona and the region, which is Spain's biggest tourist draw, it has set alarm bells ringing about the economic impact of the separatist protests.

There have been mass marches and rallies every day since the verdict was announced on Monday morning
There have been mass marches and rallies every day since the verdict was announced on Monday morning AFP / Pau Barrena

The unrest "will have a direct impact on tourism and business," warned business association Barcelona Oberta, recalling the failed referendum of October 2017 when tourist arrivals fell by 5.0 percent and turnover fell between 5.0 and 10 percent in Spain's most visited region.

Barcelona city council said Friday the first three days of clashes had cost an estimated 1,575,000 euros ($1,755,000) in damage, with more than 700 large wheelie bins torched and mob violence also damaging traffic lights, street signs, trees and the city's bike-share service.

Two cruise ships run by German tour operator TUI, each carrying 2,500 people, cancelled a scheduled stopover this weekend, although 18 others were to arrive as planned, the port authorities said.

Accounting for around 20 percent of Spain's GDP, Catalonia is heavily dependent on exports, with the CETM, which represents the transportation industry, predicting losses of 25 million euros per day due to roadblocks across the region.

Barcelona's huge wholesale market Mercabarna, which exports around a third of the region's fresh produce, was also trading at a much-reduced level on Friday, with many wholesalers and customers not showing up, a spokesman said.

And Barcelona's hotels industry said images of the ongoing violence was likely to have a "serious" impact on its tourist industry.

"Such images are especially damaging for the reputation of the city around the world and could have a serious direct impact on tourist and hotel activity in Barcelona, as well as on its socio-economic status," it said.