Gunmen from Nigeria's Boko Haram Islamist militant group killed two Cameroonian soldiers in fighting at the weekend that also left three militants dead, military officers said on Monday.
The clash highlights how pockets of Boko Haram fighters remain active despite progress this year by troops from Nigeria and neighbouring Niger, Chad and Cameroon in breaking the militants' hold on vast swathes of territory.
(READ MORE: Is Boko Haram Africa’s worst story of last decade?)
A Cameroonian officer said clashes erupted when soldiers were dispatched to check reports of Boko Haram militants moving towards the northern town of Zelevet, near the border with Nigeria.
"When we arrived ... the enemy attacked. We returned fire but sadly we lost two men," the officer said, asking not to be named. A second officer said three Boko Haram fighters were killed and a female militant captured.
Separately, a military source said another 20 people had been killed last week in attacks in villages on the Cameroon side of the border with Nigeria.
There was no immediate official comment from the military on any of the reported incidents.
(READ MORE: Nigeria's Boko Haram abducted 2,000 women and girls: report)
Earlier this year, Boko Haram occupied large chunks of northern Nigeria and was increasingly mounting attacks on neighbouring states, prompting regional leaders into action to reverse gains made by the six-year insurgency.
Operations carried out by regional forces have pushed the militants from most of their positions and Nigerian President-elect Muhammadu Buhari has vowed to crush what remains of the group.
However, Boko Haram militants continue to hit back and at least five people were killed in a raid on a village in southwestern Niger last week.