A Philippine military spokesman says seven soldiers were killed and 21 were wounded during a firefight with al-Qaida-linked militants on a remote southern island.

Lieutenant Colonel Randolph Cabangbang says the fight occurred on Jolo Island before dawn Thursday. He says the soldiers were pursuing a small group of Abu Sayyaf fighters when they accidentally came upon the rebels' main base.

Cabangbang says the discovery of the base explains the heavy casualties among the soldiers. He says the base served as the hideout of Abu Sayyaf leaders Radullan Saheron and Isnilon Hapilon, both of whom are wanted by the United States for kidnapping several Americans.

Abu Sayyaf has been implicated in numerous kidnappings, bombings and murders in the southern Philippines over the last two decades.

The group is estimated to have as many as 400 fighters, but several of its top commanders have been captured or killed in joint military operations by Philippine and U.S. forces.