Violence rocks Barcelona on fifth night of protests

The violence came after a day of largely peaceful demonstrations as more than half a million people flooded the streets of the Catalan capital to denounce the lengthy jail terms that have sent a shockwave through Spanish politics.

But as night fell, masked youths blocked a broad boulevard close to the city's police headquarters, setting fire to large garbage bins and throwing a hail of stones, cans and bottles towards massed lines of security forces in full riot gear.

Police responded with repeated volleys of foam bullets, smoke grenades and tear gas, which covered the area in thick, choking smoke.

Officials said there were clashes in at least four other towns and cities in Catalonia, Spain's wealthiest region in the far northeast of the country, as the pro-independence anger showed no sign of abating.

Spain's acting interior minister, Fernando Grande-Marlaska, said 207 police had been injured since Monday, with 107 police vehicles damaged and 800 bins burned.

Some 128 people have been arrested in the region over the past five days and Grande-Marlaska warned that the rioters faced up to six years in prison.

It is the worst such unrest Spain has seen in decades and the interior ministry sent police reinforcements to Barcelona to try to quell the chaos.