The president of Spain's powerful northeastern region of Catalonia has formally called an independence referendum in the latest secession push in Europe and one of the most serious challenges to the Spanish state of recent years.

The conservative Spanish government insists the referendum, planned for Nov. 9, is illegal and won't take place.

Catalan leader Artur Mas called the referendum Saturday, flanked by most of the region's political leaders who support the vote.

The Spanish government is expected to hold an emergency cabinet meeting Sunday on the issue. It plans to challenge a recently-passed Catalan law permitting the independence referendum before the Constitutional Court, which it hopes will suspend it and halt the vote.

The announcement comes a week after Scotland voted against breaking away from Britain.