YAOUNDE (Reuters) - Separatist militants raided a prison in northwestern Cameroon and freed about 100 inmates, the government and separatists said on Thursday, as the rebels vowed to block next month’s presidential election in English-speaking regions.

President Paul Biya is expected to easily extend his 36-year rule in the Oct. 7 vote but the insurgency by Anglophone rebels has emerged as his government’s most serious challenge in years.

The separatists complain of discrimination against English speakers in the predominantly Francophone country and want to create an independent state called Ambazonia in the oil and cocoa-producing northwest and southwest regions.

Their hit-and-run raids have killed more than 160 members of Cameroon’s security forces in the past year, Amnesty International has said. State forces have also shot at civilians from helicopters, burned villages and killed residents, forcing thousands to flee.

Nchia Martin Achuo, the head of the Tigers of Ambazonia, a separatist group that says it has around 2,000 fighters, said his men had attacked the prison in the northwest town of Wum around 4 a.m. on Wednesday and freed 106 “innocent people”.

“There was a shootout between our boys and the prison guards,” he said. “I heard that they (government soldiers) have been arresting innocent people on the street. They are not criminals in that prison.”

“NO ELECTION IN AMBAZONIA”

Government spokesman Issa Tchiroma Bakary confirmed the separatists had freed about 100 prisoners but did not provide additional details.

Martin and the leader of another separatist group, Cho Ayaba, both vowed to prevent the presidential election from going ahead in Anglophone Cameroon. Separatists have set up check points blocking traffic on major roads, helping to paralyze activity across the region.

“There will be no election in Ambazonia,” Ayaba told Reuters. “We want to make sure there is no movement from Cameroon into Ambazonia, including election materials.”

The governments in the Anglophone regions have imposed curfews and other security restrictions in recent weeks in order to contain the violence and ensure the vote can take place.

Cameroon’s linguistic divide harks back to the end of World War One, when the League of Nations divided the former German colony of Kamerun between the allied French and British victors.

Biya has ruled virtually by decree since taking office in 1982. Of Africa’s living leaders, only Equatorial Guinea’s President Teodoro Obiang Nguema Mbasogo has ruled uninterrupted for longer.