Jihadists linked to Boko Haram have killed at least 17 soldiers and 9 civilians, although some media sources such as Xinhua say the death toll has now risen to 37.
A regional security official told AFP news agency that the Boko Haram attack sparked fierce combat with Cameroonian troops in Darak, an island on Lake Chad.
He said 40 of the jihadists were captured but seven were still missing.
The insurgents managed to hoist their flag over Darak before being dispelled, AFP reports.
Boko Haram’s uprising, which has now killed more than 27,000, has spilled over from north-east Nigeria into Niger, Chad, and Cameroon.