News that there are Malaysians taking up arms to fight for the Rohingya in Myanmar's Rakhine state has raised alarm bells in the region, as it could mean the rise of another hot spot incubator for terrorism, after Marawi City in the Philippines.

Malaysian police said last week that they had detected several Malaysians who had entered Myanmar, either through Bangladesh or Thailand, to fight against Myanmar's military. And there are other Malaysians who are keen to take up arms and going to western Rakhine state.

The violence in Myanmar has led 430,000 Rohingya Muslims to flee to Bangladesh, and getting the attention of terrorist groups Al-Qaeda and the Islamic State in Iraq and Syria (ISIS), along with militants in Indonesia. At a time when ISIS is suffering losses in battles in the Middle East, security experts have for months voiced their concern that these terrorists might move their bases to jungle-clad and lightly-monitored islands in the southern Philippines or northern Indonesia.

And then in May, Marawi City on Mindanao Island was unexpectedly seized by ISIS-inspired militants. The fighting is continuing after four months and, at one point, the extremist fighters included those said to be from Malaysia, Indonesia and several Middle Eastern and Central Asian countries.

In Myanmar, the massive "clearance operations" on Rohingya villages by the military were in response to the Aug 25 attacks by Rohingya militants under the name of Arakan Rohingya Salvation Army. If the fight in Rakhine is joined by international extremists, they would have opened up a battlefield in a second Asean nation, raising the risk of radicalising more Muslims in the region.

The issue's emotional pull should be a worry for the 10-member Asean, as it could pit the group's Muslim-majority nations (Indonesia, Malaysia and Brunei) against the others. And governments with significant Muslim populations could also feel the heat on how they handle the Rohingya issue.