efe-epaZaragoza (Spain)

The mayor of Barcelona on Sunday warned the Spanish Prime Minister that if his political proposal to the controversial Catalonian independence referendum was to simply clamp down on the region, then other political parties, including his Socialist Party rivals, would seek a solution to the tension through dialogue.

Ada Colau's warning to conservative PM Mariano Rajoy came amid rising tensions in Catalonia, where separatist officials are pushing to hold a referendum on the region's independence from Spain despite it is being ruled unconstitutional by the Spanish judiciary.

Colau, the pro-independence mayor of Catalonia's largest city, said it was never too late for the Spanish Popular Party government to enter into dialogue with Catalonia's regional government but warned that if Rajoy opted not to take that approach, then regional officials would engage with Spain's opposition parties instead.

She was speaking at the opening of a political gathering in the city of Zaragoza, where members of several regional political parties met with Pablo Iglesias, the left-wing leader of Spain's third-largest opposition grouping Unidos Podemos (United We Can), to discuss the ongoing separatist developments in Catalonia.

Although the main opposition Socialist Party (PSOE) was not represented at the meeting, Colau called on its leader, Pedro Sanchez, to stop aligning the party with Rajoy's "bunkered in" PP and to assume charge of the state affairs by entering discussions.

The PP, PSOE and the business-friendly Ciudadnos (Citizens) all concur that the Catalonian independence referendum, slated for Oct. 1, should not take place.

Podemos has advocated for a diplomatic approach to the situation and has previously shown support for the legalization of a separatist bid.

The so-called O-1 referendum was written into local Catalonian law earlier this month when the bill passed through the regional parliament with the backing of Catalonia's president, Carles Puigdemont, whose Junts Pel Sí (Together For Yes, JxS) coalition holds a slim majority in the chamber.

The bill was not put before lawmakers in the national parliament and the regional legislation was suspended by the Constitutional Court, the highest rung of Spain's judiciary.

Spanish police have conducted operations in Catalonia to seize all referendum-related material.

Regional mayors who agreed to make polling stations available on referendum day were issued court summons and several senior regional government workers were arrested for their alleged role in preparing the vote _ a move that sparked mass protests in Barcelona.

Campaigning for the referendum and protests against Madrid's actions have continued.

Catalonia is a wealthy region of northeast Spain that is home to around 7.5 million people.