FRESH clashes have broken out in Barcelona tonight between riot police and Catalan independence supporters.

There were reports of tear gas being fired as thousands of people took to the streets of Catalonia's capital to protest against the jailing of nine nationalist leaders on Monday over their role in a failed bid for independence in 2017 through an unauthorised referendum.

Fugitive ex-Catalan leader Carles Puigdemont handed himself in to Belgian authorities after Spain issued a new warrant for his arrest.

Masked activists threw rocks, bottles, eggs and paint at police and set fire to large wheelie bins as violence erupted tonight.

READ MORE: Europe must condemn repression of the Catalans

Police in riot gear retaliated by firing rubber bullets and smoke grenades and using batons.

Spain's interior minister Fernando Grande-Marlaska - the equivalent of the UK Home Secretary - warned protesters they could be jailed for up to six years.

Earlier some 500,000 people had gathered to march peacefully through the city, bringing streets to a standstill and leading to a reduced train and metro service.

Catalan regional leader Quim Torra thanked those who had demonstrated peacefully and criticised the rioters.

READ MORE: Blocking indeyref2 indefinitely 'unsustainable'

"There is no space for impunity in relation to the serious acts of violence we have witnessed over recent days in different cities in Catalonia," he said.

Barcelona's iconic Sagrada Familia church was closed after protesters blocked its entrance, and nearly 100 people have been reported injured.