The soldiers were part of a military offensive against the terrorist group ordered by the Filipino President Rodrigo Duterte six days ago.
They were killed in a fierce gunbattle Monday in the Abu Sayyaf stronghold town of Patikul, less than 10 kilometers (6.2 miles) from Jolo, the capital of Sulu province, the military's Western Mindanao Command center based in Zamboanga City declared in a formal reports to local media.
Abu Sayyaf is one of the smallest and most violent terrorist groups linked to ISIS and is based in the southern Philippines. It is notorious for kidnapping, ransom, and attacks on civilians and the army. In 2004 it bombed a ferry in Manila Bay, killing 116 people.
In the last year it has taken several people hostage - Malaysian and Indonesian workers, Western tourists and one Filipina among them.