Tens of thousands of Spaniards took to the streets in Madrid on Sunday to protest against reports that acting Prime Minister Pedro Sanchez could grant amnesty to Catalan separatists in return for political support.

Protesters chanted "out, out" and "Sanchez, resign."

Authorities estimated the turnout to be 40,000 people while the conservative People's Party (PP), which organized the event, said around 60,000 protesters attended.

A number of PP figures participated on stage including Madrid Mayor Jose Luis Martinez-Almeida and regional president Isabel Diaz Ayuso, as well as two of Spain's former leaders, Mariano Rajoy and Jose Maria Aznar.

Why are there reports of an amnesty deal?

Although PP leader Alberto Nunez Feijoo won the Spanish election in July, his party along with the far-fight Vox party and two smaller conservative parties fell four seats short of achieving a majority in parliament.

Meanwhile, Sanchez could secure enough votes in parliament to stay in office if he wins the support of the country's regionalist political parties.

Chief among them is Junts per Catalunya led by exiled former Catalonia leader Carles Puigdemont. The party holds seven seats.

Puigdemont, who is wanted in Spain for attempting the region's secession in 2017, has demanded that legal action be dropped against fellow separatists as a condition for his support.

Sanchez is reportedly considering such a deal but has not made any announcements.

The lower house of the Spanish parliament will vote on Feijoo's candidacy for prime minister on Tuesday.

His bid is widely expected to fall short, paving the way for Sanchez to put forward his candidacy.

zc/nm (Reuters, dpa, AFP, EFE)