BARCELONA, Sept. 30 (Xinhua) -- Thousands of people took to the streets of Barcelona on Saturday to defend Spain's unity, its constitution and protest against the independence referendum set to be held on Sunday which has been declared illegal by Spain's Constitutional Court.

The demonstration was organized by associations against the referendum. It started at 5:30 p.m. local time from one of the main squares of the city, Plaza Urquinaona, and ended in Plaza Sant Jaume where the regional government of Catalonia, Generalitat, and Barcelona's city council, are located.

People shouted slogans like "we will not vote", calling for sending Catalan regional leader Carles Puigdemont to prison for being part of the organization of an illegal referendum.

Paco Ortiz told Xinhua, "This is Catalonia and at the same time this is Spain, and this is how most of us we feel".

In Madrid, the capital of the country, several thousand people also demonstrated outside of the Madrid City Hall on Saturday in protest against the referendum.

The government delegate in Madrid estimated that around 10,000 people took part in the demonstration to vindicate the "unity of Spain."

The demonstrators shouted slogans such as "Spain united will never be defeated."