Local police were deployed in a security ring around a section of the park where Catalonia’s parliament building is located behind walls. Puigdemont walked towards the building followed by masses of supporters.

He had earlier announced publicly that he was returning to Spain, though he gave no travel details.

Puigdemont’s presence in Spain is likely to generate renewed political tension over the smoldering issue of Catalan independence. The failed secession attempt triggered a protracted constitutional crisis.

It was not immediately clear how authorities will proceed if he is arrested.

A contentious amnesty Bill, crafted by Spain’s Socialist-led coalition government, could potentially clear him and hundreds of other supporters of Catalan independence of any wrongdoing over the illegal 2017 ballot.

But the Bill, approved by Spain’s parliament earlier this year, is being challenged by the Supreme Court, leaving uncertainty about what crimes would be pardoned. Puigdemont could initially be placed in pre-trial detention if he is arrested.

The former Catalan leader’s return threatened to complicate a deal brokered after months of deadlock between Salvador Illa’s Catalan Socialist Party (PSC) and the other main Catalan separatist party and left-wing Esquerra Republicana (ERC).

That deal had ensured just enough support in Catalonia’s parliament for Illa to become the next regional president in an investiture debate on Thursday.