Hundreds of thousands of demonstrators gathered in the Spanish city of Barcelona on Saturday evening to demand autonomy for the north-eastern region of Catalonia, dpa reported.
Police estimated that some 1 million people participated in the rally, which featured the slogan "We are one nation. We decide."
The demonstrators were protesting a recent decision by the Spanish Constitutional Court that struck down some of the articles in a statute increasing the region's self-government.
The protest was led by Catalan President Jose Montilla.
Participants made their way through the centre of the city, waving Catalan flags and chanting independence rallying cries. Banners proclaimed "Adeu Espanya" - Bye, Spain.
Not all protesters, however, were calling for the economically strong region to become autonomous. Instead, they demanded a repeal of the Constitutional Court's decision.
The judges had, among other things, rejected the intended creation of a Catalan justice system. They also deemed a plan for the Catalan language to have precedence over Spanish in schools and the administration to be unconstitutional.
The most contentious article classified Catalonia as a "nation." The judges accepted the measure, but downgraded it by stressing that the definition does not have legal value.
The autonomy statute grants Catalonia's 7.5 million residents increased political and economic autonomy. It had previously been approved by the Catalan regional parliament in 2005, followed by the Spanish parliament and a Catalan referendum a year later.
But Spain's main opposition People's Party had lodged a court appeal against the statute, arguing that it endangered Spanish unity.