Fugitive former Catalan separatist leader Carles Puigdemont returned to Spain after seven years on Thursday before disappearing again.

The former regional leader had fled Spain over his role in a failed 2017 independence bid despite a pending arrest warrant.

Puigdemont shouted "Long live a free Catalonia!" as he climbed onto a stage in Barcelona to address thousands gathered near the Catalan regional parliament, which is set to elect a new leader later in the day.

"I have come here to remind you that we are still here," he said as many in the crowd waved red, yellow and blue Catalan independence flags.

After his brief address, Puigdemont appeared to head towards the nearby Catalan parliament but the assembly began an investiture vote to pick a new leader for the region without him being present.

It was not immediately clear where he was.

Police had set up roadblocks in Barcelona and were searching cars to try to find Puigdemont, according to Spanish media reports.

Contacted by AFP, police declined to comment if such an operation was underway.

Nuria Pujol, a woman in her fifties who came to Barcelona from the Alt Penedes region to see Puigdemont, called him "a very noble person."

"(He's) the only one who believes in independence and has not stopped believing," she added.

A small group of protesters gathered nearby, waving national Spanish flags and holding signs that read "Catalonia is Spain," in a demonstration organized by far-right party Vox.

'Problem with democracy'

Puigdemont's dramatic return came just days after Spanish Prime Minister Pedro Sanchez's Socialists struck a deal with moderate Catalan separatist party ERC – which competes with Puigdemont's more hardline JxCAT – to make the Socialist candidate, Salvador Illa, the next head of the Catalan regional government.

The Socialists won the most seats in a regional election in May but failed to get a majority and the support of the ERC is crucial.

If a new Catalan regional government is not formed by Aug. 26, fresh elections will be held in October.

Puigdemont led the regional government of Catalonia in 2017 when it pushed ahead with an independence referendum despite a court ban, followed by a short-lived declaration of independence.

He fled Spain shortly after the independence bid to avoid prosecution and has since lived in Belgium and more recently France.

While Spain's parliament in May passed an amnesty law for those involved in the botched secession bid, the Supreme Court ruled on July 1 that the measure would not fully apply to Puigdemont.

"A country that has an amnesty law and does not apply it, has a problem with democracy," he said in his speech.

Path to independence?

Sanchez agreed to the amnesty law in exchange for JxCAT's crucial support in Spain's parliament for his fragile minority government, sparking huge street protests that were organized by the right wing.

He is now facing opposition from parts of his own Socialist party as well as the right over a proposal to give Catalonia full control of the taxes collected in the region.

The measure was promised to the ERC in exchange for the party's support for Illa in Thursday's Catalan investiture vote.

The proposal has for decades been one of the main demands of Catalan independence parties but critics argue it would deprive the central state of a substantial source of revenue.

It must still be approved by Spain's national parliament.

A similar system already exists in Spain's northern Basque Country, which also has an active independence movement.

If Illa passes Thursday's investiture vote, he will be the first head of Catalonia's regional government since 2010 who does not come from the separatist camp.

The former health minister has defended the tax agreement made with the ERC, saying it was "favorable for all Catalans."

"They are agreements designed to improve our finances without harming anyone and whilst respecting the principles of (fiscal) solidarity," he said after securing the ERC's support.

But former Socialist deputy prime minister Alfonso Guerra has said the tax agreement opens "a path towards a federal system and the independence of Catalonia."