The attack just a few kilometres from the Nigerian border came as Cameroonian soldiers were taking two suspected Boko Haram militants in for questioning.
"As they were taking them by foot to their base, other Boko Haram militants came to save their comrades," said a police officer speaking on condition of anonymity.
"They shot at the soldiers," he said, adding that three soldiers were wounded.
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The new attack came as the Cameroonian army was deploying reinforcements to northern regions bordering Nigeria, in a bid to contain the Boko Haram threat.
"The deployment is badly seen by Boko Haram. They have threatened to bury mines in the region to blow up convoys of our security and defence forces," a security source in the region said.
More than 1,000 soldiers are being deployed to the Waza region, where 10 Chinese nationals were recently kidnapped by Boko Haram militants, sources said.
The cross-border attack in mid-May hit a camp where the Chinese road workers were staying.
