As Catalonia prepares to declare independence tens of thousands of people are gathering in Madrid and Barcelona, many dressed in white and calling for talks to defuse Spain's worst political crisis for decades.

The wealthy northeastern region of Catalonia, with its own language and culture, has long claimed to be distinct from the rest of the country and last weekend held a referendum on leaving Spain, a vote the constitutional court had banned.

The Catalan authorities say that a majority of those who voted supported a split from Spain. Madrid says secession is illegal under the country's 1978 constitution.

The political stand-off has divided the country, pushed banks and companies to move their headquarters outside Catalonia and shaken market confidence in the Spanish economy, prompting calls from the European Commission for Catalan and Spanish leaders to find a political solution.

In peaceful protests called across 50 Spanish cities, and fully dispersed by early Saturday afternoon, thousands gathered dressed in white and carrying banners calling for peace and dialogue between leaders.

In Barcelona, protesters chanted "let's talk" in Catalan, while many carried signs criticising political leaders for not finding a diplomatic solution to the impasse.

While Catalan leader Carles Puigdemont has said he is open to mediation, Prime Minister Mariano Rajoy insists he gives up the independence campaign, which grew in strength during a near-six year economic crisis, before discussions can be held.

Meanwhile, in Madrid, parallel to the "Let's talk" march, thousands gathered beneath the enormous Spanish flag in Colon Plaza waving their own flags, singing and chanting "Viva Espana" and "Viva Catalonia".

Rajoy's government mobilised thousands of national police to stop last Sunday's vote, leading to clashes with would-be voters as they tried to close polling stations in schools and remove ballot boxes. Nine hundred people were injured on polling day.

Some EU states are worried that talk of Catalan independence could fuel secessionist feelings in other parts of Europe.