Spain's Prime Minister Pedro Sanchez and the opposition leader visited Barcelona on Monday to meet police struggling with Catalan separatist violence in a crisis that could be a game-changer in next month's general election.

The visit came as Sanchez faces mounting criticism over his handling of the crisis, which erupted a week ago when the Supreme Court sentenced nine separatist leaders to lengthy jail terms over an abortive 2017 independence bid.

Over the past week, nearly 600 people have been hurt, two of whom remain in critical condition, as protesters have torched cars, burnt barricades and lobbed rocks at police who have hit back with tear gas and rubber bullets.

Spanish Prime Minister Pedro Sanchez went to visit some of the injured police officers at a Barcelona hospital / © LA MONCLOA/AFP

The nightly violence has dominated the news in Spain and made headlines around the world, but so far, Madrid has shown little appetite for direct intervention, despite repeated calls for regional president Quim Torra to condemn the unrest.

And the crisis has done little to help the ruling Socialists, with a string of surveys on Monday showing rising support for the conservative opposition Popular Party.

If an election was to be held today, the Socialists would win 117 seats in the 350-member parliament, down from 123 in tha April elections, while the PP, would take 103 up from 66 in April, according to a poll in

- 'Oust Torra, suspend autonomy' -

In an address at the police headquarters, Sanchez acknowledged the crisis was not yet over but warned the government would not back down.

"It is evident that the radicals who engage in violence have decided that Barcelona will be their theatre of operation to broadcast their grievance to those at home and abroad," he said before meeting wounded officers in hospital.

"While it's true that the crisis isn't over, we have to keep trying. They want to make it worse but we are much more persistent, much more determined."

PP head Pablo Casado used his visit to Barcelona to demand the government "intensify its operations" against the troublemakers, urging it to ensure the "immediate return of security... to the streets of Catalonia".

Sanchez has repeatedly come under fire from his opponents for taking a soft line on the separatists, with the resolutely anti-separatist Ciudadanos on Sunday demanding Madrid oust Torra and suspend Catalonia's autonomy, as it did in 2017.

So far, Sanchez has refused to speak to Torra despite his call for "unconditional" talks, an apparent attempt to secure agreement for a legal referendum on independence -- a non-starter for Madrid, which claims the Constitution does not allow it.

- 'Sit down and talk' -

But former Catalan vice president Oriol Junqueras who last week was handed the heaviest sentence of all the separatist leaders -- 13 years in jail -- said the only answer was a political solution.

On Monday protesters in barcelona urged the Spanish government to engage in talks / © AFP

"The way to end these clashes is through politics, through channelling the feeling and wishes of all these people who want a political solution to the conflict," Junqueras told TV3 television in a written interview.

"The state must sit down at the table and talk about how to find a political solution."

Catalan interior minister Miquel Buch told journalists it was unacceptable for Sanchez to ignore Torra's overtures, insisting he "sit down and talk: political problems are resolved through politics".

The same message was coming from the streets.

Standing outside the Spanish government's delegation in Barcelona with a group of some 500 protesters, Montse Serra, 53, said it was time for Sanchez "to face the music".

"If the state does not want to talk, we have to force it, even if it makes things worse. We have to force it to negotiate," she told AFP.

Although Barcelona returned to relative calm at the weekend, some 500 activists Monday rallied in the city centre demanding Sanchez "sit and talk".

In the evening hundreds of protesters gathered outside an interior ministry building in Barcelona for a rally called by the radical separatist group CDR. Some threw paint-filled balloons at police vans parked outside.