The clash occurred at 1.15 a.m when the rebels from Bangsamoro Islamic Freedom Fighters (BIFF) attacked a reconnaissance company of the 61st division of the Philippines military in North Cotabato province, Xinhua reported.
"Seventeen BIFF members were killed. We have identified five of them," the official said.
"One soldier was also killed," the official added.
The BIFF, founded by former Moro Islamic Liberation Front (MILF) commander Ameril Umbra Kato, defected to the MILF in late 2010 after the latter decided to drop its call for an independent Islamic state.