The parliament of Spain's Catalonia region is set to elect a new leader this week, although the event may be upstaged by the return of its former leader from self-imposed exile, despite a pending warrant for his arrest, Paralel.Az reports citing Reuters.

Carles Puigdemont is the figurehead of hardline separatist party Junts, and led Catalonia between 2016 and 2017 before fleeing Spain following a referendum on independence deemed illegal by the judiciary.

It remains unclear how he plans to return to the country and enter the regional parliament while evading police.

Jordi Turull, secretary-general of Junts, told broadcaster 324 on Tuesday that he would call for the leadership vote to be suspended if Puigdemont is detained, as "it cannot take place in normal conditions" without him present.

The vote to invest Socialist Salvador Illa, who will be backed by the left-wing separatist ERC party after a bilateral deal last week, will kick off on Thursday at 10 a.m. local time (0800 GMT), according to the parliamentary speaker.

The Spanish parliament passed an amnesty law in May pardoning those involved in the failed 2017 secession bid, but the Supreme Court upheld arrest warrants for Puigdemont and two others, who were also charged with embezzlement, ruling that the amnesty law does not apply to them.

A source close to Puigdemont told Reuters he had "no doubt" that the former leader - who lived in Belgium between 2017 and 2024 while serving as a member of the European Parliament and has in recent months been based in southern France - would be arrested upon re-entering Spain and brought before the Supreme Court in Madrid.

Political scientist Toni Rodon of Barcelona's Pompeu Fabra University told Reuters that Puidgemont had possibly decided to come back because of the personal toll of living in exile.

"The amnesty has changed the game play, and the other strategy he can pursue can be more useful inside the Spanish borders even if he ends up in jail," Rodon added.

In an open letter posted on his X account on Friday, Puigdemont described Spain's efforts to detain him as a "hybrid coup", adding "if they succeed, I imagine what awaits me and know what I must do".

ERC spokesperson Raquel Sans acknowledged on Tuesday that Puigdemont's arrest could delay the vote for a new Catalan leader.

Police will try to arrest Puigdemont before he reaches the heavily guarded parliament building in Barcelona, but are also authorised to enter if needed, El Periodico newspaper reported, citing police sources.

Officers were also monitoring the sewer system in case it was used for alternative entry routes.

In 2011, then-leader Artur Mas was forced to access the building's rooftop by helicopter after it was surrounded by nearly 1,000 anti-austerity activists protesting against budget cuts.