The far north of Cameroon has become a hotbed of Boko Haram activity, with its porous borders making it an easy staging post for attacks and kidnappings in Nigeria.
A mixed squad of soldiers and paramilitary officers were patrolling the area around the town of Mora when they came across "a dozen Islamists," the officer from regional capital Maroua said on condition of anonymity.
"Clashes broke out and our forces got the upper hand. Eight Boko Haram were killed," he said.
"Seventeen are still in custody. Most of the suspects are Nigerians," who had false Cameroonian identity documents, the officer said.
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The operation took place after police received a tip-off that "allies of Boko Haram had moved into Maroua as hairdressers".
Cameroon shares a border of more than 2,000 kilometres with Nigeria. The Islamist militants have already kidnapped several foreigners there.
In mid-May, suspected gunmen from the group took 10 Chinese road workers captive in an attack which left a Cameroonian soldier dead.