The Philippines' largest Muslim rebel group has condemned extremist jihadists in Iraq and Syria, and vowed to stop the spread of their "virus" into the Southeast Asian nation.

After decades of armed rebellion that claimed tens of thousands of lives, the Moro Islamic Liberation Front (MILF) signed a peace agreement in March that commits it and the national government to share power in the area.

The MILF portrayed its moderate leadership as vital to stopping the savage ideology of Islamic State (IS) infecting the southern Muslim regions of the mainly Catholic Philippines.

"The MILF condemns barbarism and savagery whether done by other groups including the ISIS or even by its (MILF's) own members," the MILF said in an editorial posted on its www.luwaran.com website this week.

"Frankly, it is the power, moderating line, and influence of the MILF that hinders the birth of a truly strong radical group."

The MILF also said a planned Muslim autonomous region that is the centrepiece of the peace deal would be a bulwark against the ideology of the Islamic State, which is also known as ISIS.

The MILF urged President Benigno Aquino to approve a draft bill to create the autonomous region, which was submitted to him last week by a joint committee of rebel and government negotiators.

The peace agreement had called for Aquino to submit the bill to Congress earlier this year, so the autonomous region would be in place by the time he leaves office in mid-2016.

But he rejected an earlier draft and had the joint committee prepare a revised version.

"It is this... fear (of) not being able to realise it (passage of the Muslim autonomous law) for whatever reason that the ISIS' virus is much to be feared," the MILF warned.

Two other Filipino Muslim armed groups, the Abu Sayyaf and the Bangsamoro Islamic Freedom Fighters (BIFF), have recently vowed allegiance to the IS in video clips uploaded on the Internet.

Some politicians have expressed concern both groups may be sending recruits abroad to fight alongside the IS, though the Philippine military said there was no evidence of this.

The Abu Sayyaf is a loosely organised Al-Qaeda-linked group of several hundred militants blamed for the Philippines' deadliest terrorists attacks.

The BIFF, which has about 200 fighters, split from the MILF after rejecting peace talks and has vowed to continue pursuing an independent Islamic state.

"For us, the threat is not in the two groups' joining the ISIS. Their number(s) (are) too tiny to be felt and make a difference," the MILF said.

"The threat really comes from the extremism espouse(d) by the ISIS. Ideas are contagious and infectious."