BARCELONA, Spain (AP) — Advocates of independence for Spain's northeastern region of Catalonia have launched their campaign to try to elect a majority of secessionists in regional parliamentary elections on Sept. 27.

The campaign began Friday on the same day as the Catalan National Day holiday that separatists have used for years to rally hundreds of thousands of people in Barcelona to call for the creation of a new Mediterranean nation.

Pro-independence parties need 68 seats in the 135-member parliament to push their effort forward. Polls show them on track to win a slim majority.

They say a win would put Catalonia on a path toward a unilateral declaration of independence in 18 months.

The central government in Madrid says independence for the region is illegal and won't be allowed.