MANILA, Feb. 18 (Xinhua) -- A junior army officer and four soldiers were wounded on Sunday in an attack in the southern , a military spokesman said.

Capt. Arvin Encinas said the troops were aboard a military truck on an "administrative mission" when attacked around 7:30 a.m. in Meta village in Datu Unsay town in Maguindanao province.

He said an improvised explosive device went off as the truck approached a bridge.

"They were mobile and as soon as they reached the bridge in barangay meta, they were hit by IED explosion. There was no firefight, it's merely an IED explosion aimed at our troops," Encinas said.

The military blamed the attack on Bangsamoro Islamic Freedom Fighters (BIFF), a group of about 300 militants that also pledged allegiance to the Islamic State extremists.

Encinas said the attack was a revenge to the ongoing military offensive against the BIFF that started in August last year.