The Philippine military has used aircraft and artillery to attack a group of Muslim extremists who were learning how to make improvised explosive devices, a spokesman said Sunday.
The attacks between March 13-16 were a severe blow to fighters of the Bangsamoro Islamic Freedom Fighters (BIFF), some of whose members have pledged allegiance to the Islamic State group, said Brigadier General Restituto Padilla.
"The target was completely destroyed," he told AFP following assaults by planes, helicopter gunships and artillery in the southern island of Mindanao.
There were no civilians in the area during the attack, he said.
Foreign and local extremists were meeting in a BIFF enclave in the southern province of Maguindanao when the attack was launched, Padilla said, declining to say where the foreigners had come from.
He cited intelligence sources as saying 21 extremists were killed and 26 wounded, although no bodies were recovered.
Muslim rebels often carry away their dead and wounded.
Five completed improvised explosive devices were recovered along with bomb-making manuals and materials, the military said.
Troops are still tracking down the remnants of the BIFF group, Padilla said.
Muslim rebels have waged a separatist insurgency in the south of the mainly Catholic Philippines since the 1970s, with the conflict claiming more than 120,000 lives.
While the major rebel organisations have for years observed a ceasefire as part of peace efforts, breakaway factions like the BIFF and other Muslim gangs still engage in bombings and kidnappings.