Clips have been uploaded in recent weeks on the video sharing site YouTube showing both southern Philippines-based Bangsamoro Freedom Fighters and the Abu Sayyaf rebels pledging support to ISIL.
"We have an alliance with ISIL and Abu Bakr al-Baghdadi," BIFF spokesman Abu Misry Mama told AFP by telephone Friday, referring to the brutal radical group's leader.
Misry confirmed that a YouTube video uploaded Wednesday, showing a purported BIFF leader flanked by armed men reading a statement of support for the ISIL, had come from his group.
BIFF split in 2008 from the Philippines' main Muslim rebel group, the 12,000-member Moro Islamic Liberation Front. The latter signed a peace agreement with President Benigno Aquino's government last March.
BIFF, which is believed to have a few hundred fighters, has rejected the peace talks and pursued the decades-old armed campaign to establish a state in the southern Philippines which was begun by the MILF.
Abu Misry, described by the Philippine military as a BIFF spokesman, said his group had no plans to impose the radical ISIL brand of Islam in the Southeast Asian nation.
Beheadings, mass executions and the taking of child brides have marked the ISIL militancy across large parts of Iraq and Syria.
Abu Misry said his group had not sent any fighters from the Philippines to help ISIS, nor was it recruiting people to join ISIL.
"But if they need our help, why not?" he added.
Colonel Dickson Hermoso, spokesman for a southern Philippines-based army division, described BIFF as a "terrorist" group engaged in extortion to finance its activities.
"There's no evidence that Filipino fighters are being sent there (to Syria and Iraq)," Hermoso told AFP, while adding that both BIFF and ISIL followed an "extreme" brand of Islam.
A purported Abu Sayyaf video has also been uploaded on Youtube showing one of the group's most senior leaders, Isnilon Hapilon, mentioning Baghdadi as he read out a statement that pledged allegiance to ISL.
He was filmed linking arms with more than a dozen men, some with faces swathed in fabric, as they stood at a forest clearing to pray and listen to his statement.
Hapilon carries a $5 million reward on his head by the United States which considers his group a "foreign terror organization" engaged in beheadings, bombings, and kidnappings.
Philippine military spokesman Lt. Col. Ramon Zagala dismissed the video clips.
"This is propaganda and we will not give these terrorists the satisfaction by commenting," Zagala told AFP.
SHI/SHI