BORDEAUX, France -- French police defused a bomb at the local headquarters of the Socialist Party in the southwestern town of Bayonne, in the heart of France's Basque country, Reuters reported.

No group had claimed responsibility for the bomb, which police said could have caused extensive damage, had it exploded.

French Basque separatists have stepped up attacks against central government buildings in the region this year in a drive for an independent Basque nation carved out of southwest France and northern Spain.

Police said on Sunday a neighbor had discovered the homemade device on Saturday evening. It had been planted on the first floor of a building in the center of the town.

"We are not ruling out any lead. This could have had serious consequences as people live in that building," a local policeman said.

A number of French Basque separatist groups have carried out attacks in the region that cause material damage.

The Spanish Basque guerrilla group ETA, which has been blamed for more than 800 deaths in Spain, has used France as a base to plot bombings and assassinations and weapons or members on the run.