DAKAR, Dec 31 (Reuters) - Suspected separatists in Senegal's restive Casamance province killed a prominent local ruling party official by slitting his throat late on Saturday, ahead of the Muslim Eid al-Adha feast, a security force official said.

Armed men attacked Oumar Lamine Badji, president of the regional council of President Abdoulaye Wade's ruling Democratic Party (PDS), at his family home in the village of Sindian, around 50 km (30 miles) from the provincial capital Ziguinhor, the official said.

"They came to Badji's home. They set his house on fire and fired shots nearby, and then slit his throat," the security force official in Ziguinchor, who declined to be named, told Reuters.

Security forces suspected the assailants were separatist rebels, he said.

Prime Minister Macky Sall deplored Badji's killing in a broadcast on state radio, but did not comment on who was responsible.

Badji's killing happened the night before Senegal's overwhelming Muslim majority celebrated Eid al-Adha, known locally as Tabaski, when Muslim families kill sheep, generally by slitting their throats.

Casamance, Senegal's only predominantly Christian province, has seen more than two decades of low-level insurgency by the rebel Movement of Democratic Forces of Casamance (MFDC), who seek independence.

Residents of the southern province, which is separated from the rest of Senegal by the former British colony of Gambia, complain of being marginalised.

Violence has subsided in recent years as President Wade's government has renewed peace efforts, but fighting intensified in mid-2006 when government forces from Senegal and neighbouring Guinea Bissau, along with moderate MFDC factions, battled an armed MFDC wing which rejects peace talks.

Senegal, one of the few African countries never to have had a coup d'etat, is regarded by foreign donors as a bastion of democracy in an unstable region. Wade, 80, is to seek a second and final term in office in elections in February