Fugitive former Catalan leader Carles Puigdemont handed himself in to Belgian authorities on Friday, as violent protests continue to rock Catalonia. 

It comes after a new warrant for his arrest was issued by Spain, following the sentencing of 12 of his former colleagues.  

Puigdemont and several of his associates fled to Belgium in October 2017 after they were summoned to court over the secessionist push he led and the holding of an independence referendum that the Spanish government said was illegal. 

A general strike is expected in Catalonia on Friday, following violent clashes for a fourth consecutive night in Barcelona between pro-independence demonstrators and Spanish police. 

Friday's strike is expected to cause major disruption to trains and other public services. 

Protesters are expected to march from across the Catalan region on Friday, aiming to meet in Barcelona at approximately 15:00 local time. It marks the fifth day of protests over the conviction of a dozen Catalan independence leaders. 

Spanish authorities are preparing to send in reinforcements over the weekend to quell the unrest.

On Thursday, thousands of students took to the streets in peaceful protests, but violence later broke out between Spanish nationalists and police forces. 

A small group of protesters continued to demonstrate into the early hours of Friday morning. Spanish authorities said this group set fire to a shop, vandalized a bank and threw stones and petrol bombs. 

Spanish nationalists sang fascist songs and chanted "Heil Hitler", while performing the Nazi salute. 

One pro-independence activist was badly beaten by self-identifying alt-right wingers and several people were treated for injuries, according to emergency services. 

Catalonia's president Quim Torra condemned the violence. In a televised statement on Thursday, he called on protesters to demonstrate peacefully. 

Catalan opposition members of parliament have called for the president to resign, criticizing the way he has handled the unrest and calling his actions "a failure."

On Wednesday, Catalonia's jailed politicians also urged the public to protest peacefully, after the Spanish government threatened a "firm" response to the street chaos. 

Protests broke out on Monday, hours after the Spanish Supreme Court sentenced nine of the 12 Catalan politicians and activists to between nine and 13 years behind bars, following Catalonia's 2017 failed independence referendum.  

The court found them guilty of sedition, disobedience and misuse of public funds. Four of them were additionally convicted of misuse of public funds. The other three were fined for disobedience and the court barred all of them from holding public office.

Among those jailed was the former Catalan vice president, Olio Junqueras, who received a 13-year prison sentence.