ONITSHA, Nigeria (Reuters) - Cameroonian troops crossed into neighboring Nigeria in pursuit of separatist rebels, a Nigerian state defense spokesman and a former community leader said on Wednesday.

Cameroon has been fighting Anglophone separatists who have taken up arms over the past year in an attempt to create a nation which they call Ambazonia. The insurgency represents the gravest challenge yet to the 35-year rule of Cameroon’s President Paul Biya.

More than 43,000 Cameroonians have fled as refugees to Nigeria to escape the government crackdown on the separatists, say local aid officials. The majority are in Nigeria’s Cross River state, which borders southwest Cameroon.

A spokesman for Nigeria’s civil defense agency in Cross River state said Cameroonian gendarmes crossed into Danare, a border community in the Boki local government area of Cross River state, on Tuesday. He said they harassed Cameroonian refugees and their Nigerian hosts.

“The gendarmes came in briefly, harassed the people and left immediately. They have been doing this since the crisis of agitation for independence forced these refugees to flee Cameroon and come into Nigeria,” said Solomon Eremi, a spokesman for the Nigeria Security and Civil Defence Corps (NSCDC).

A former councillor in Boki, Douglas Ogar, also said Cameroonian gendarmes had entered the community. “The gendarmes are so emboldened as they have shown outright defiance to Nigeria’s territorial sovereignty,” he said.

“The government does not comment on rumors,” said Cameroon government spokesman Issa Tchiroma Bakary when asked about claims that gendarmes had entered Nigeria.

It is not the first reported incursion by Cameroonian gendarmes. At least one such move was carried out by troops last month.

Last week, a Cameroonian separatist leader arrested in Nigeria’s capital, Abuja, was deported.

The linguistic divide in Cameroon - a mostly Francophone country - harks back to the end of World War One when the German colony of Kamerun was carved up between allied French and British victors.

The English-speaking regions joined the French-speaking Republic of Cameroon the year after its independence in 1960. French speakers have dominated the country’s politics since.