Catalan regional government President Artur Mas has officially called early elections for Sept. 27, a poll he intends to use as a referendum on independence from Spain.

Mas signed the election bill late Monday saying Spain's decision not to allow the region hold an independence referendum last year left it with no choice but to call elections and use them as a test of public opinion.

Mas' ruling Convergence party and the region's second party, the Republican Left of Catalonia, are running joint candidates and say they will unilaterally leave Spain if they obtain a majority.

Spain has ruled out any possibility of secession.

Recent opinion polls show a slim majority of Catalan voters oppose independence.

Catalonia, whose capital is Barcelona, accounts for about one-fifth of Spain's gross domestic product.