A statement from the office of Spain’s caretaker prime minister said 33 people have been arrested. Four protesters have been jailed so far on provisional public disorder charges.
The Spanish leader, Pedro Sanchez, is meeting experts from the interior and other ministries to analyse the security situation.
It came as Thursday began with new road blockades across the north-eastern region, including a main highway leading to France.
Rioting raged in Barcelona and several other Catalan towns for a third night, with police fighting running battles with protesters angered by lengthy prison sentences for nine leaders of the region’s drive for independence from Spain.
Tens of thousands of protesters faced off against police in Barcelona. Some set up flaming barricades in the streets, torching cars and bins, chanting: “The streets will always be ours!”
Police said protesters threw petrol bombs, stones, bottles and fireworks at them.
Violence erupted on Monday after Spain’s Supreme Court sentenced nine separatist Catalan leaders to up to 13 years in prison for their part in an October 2017 effort to declare independence for the region.
After a surge in separatist sentiment since the global economic crisis that hit Spain particularly hard, around half of Catalonia’s 7.5 million residents want to break away from Spain and forge a new European country.
The issue has divided families and friends, but demonstrations had largely been peaceful until this week.
Outnumbered police used helmets, vests and shields for protection. They fired foam bullets and swung batons to keep away the swarming radicals, most of whom covered their faces. Police also drove armoured vans at high speeds to scatter the crowds.
One police helicopter was hit by five “pyrotechnic” objects similar to fireworks, according to the regional police force.
Central Barcelona, a leading tourist destination known for its beautiful architecture and relaxed atmosphere, became a no-go territory.
Health services in Catalonia said medics attended to 52 people in the region on Wednesday. Police said late in the evening that they had arrested “at least 20 people” throughout Catalonia for violent acts.
Mr Sanchez said the clashes would not provoke him into taking drastic measures in Catalonia, despite calls by rival parties to crack down on the separatist politicians in the region.
The PM, who is in interim charge while awaiting national elections on November 10, consulted other national political leaders in Madrid during the day about the trouble.
The Spanish government will respond with “firmness, calmness and unity” to the confrontations, he said in a televised address.
He blamed “organised groups of extremists” for the rioting but said he would not be drawn into playing their game of an “ascending spiral of violence”.
The protests followed the pattern of previous days as crowds gathered during the day to block roads and hold marches demanding independence. After sunset, the marches turned ugly.
Police also reported clashes in Girona, a town near the French border, and other places.
On Monday police skirmished for hours to keep protesters from entering Barcelona’s main airport and shutting it down.
An organisation representing Barcelona businesses, called Barcelona Abierta, said the violence had caused “significant losses” and “deeply damaged” its image abroad.
Other protests are scheduled in the coming days as separatists vow no let-up in their secession drive.