Is historical claim behind the mystery group of (armed?) Filipinos in Borneo?

It's around an hour by speedboat from Sulu in the southern Philippines to Sabah in the Malaysian part of Borneo, a route often plied by fishermen, traders, and migrants. The maritime route goes from what is the poorest part of the Philippines to eastern Malaysia, and many make the journey in search of work.

But when on Tuesday around 100 men arrived in batches to – and depending on what account you read – camp out in, or occupy a village called Lahud Datu, it soon become clear these weren't the usual fishermen or migrant workers.

What exactly is going on is unclear, but it has both countries on high alert. Malaysian security forces have sealed off the village, which is 300 miles from Sabah's regional capital Kota Kinabalu, a two-hour flight from Malaysia's main city Kuala Lumpur.

On Thursday, Malaysia's Home Affairs Minister Hishamuddin Hussein said that Malaysian security forces had cornered the group, said to be armed. By Friday, however, the Sabah police chief was reportedly negotiating with the men, some of whom were claiming to be descendants of the Sultan of Sulu and therefore, they said, entitled to land in this part of Malaysia.

What is the Sultanate, anyway?

The sultanate, or the territory the sultan governed, existed from the late 15th century until the late 19th century, governing Muslims spanning parts of Sulu and northern Borneo.
  
Though the sultanate is not recognized anymore internationally as a governing entity, Malaysia still pays a token "rental fee" to the heirs of the last sultan.
  
The claims could put the Philippines in an awkward position, embroiled in an unwanted territorial dispute, given that the men camped out in Lahud Datu are Filipino nationals.

Who are these men?

Though it’s unclear who this “royal army” is, analysts are eyeing three southern Filipino militias. Militants from the southern Philippines have a history of crossing the narrow stretches of water to Borneo.
  
Some speculated at first that the groups' appearance had something to do with deadly clashes in early February between the Moro National Liberation Front (MNLF) and Abu Sayyaf, two Muslim armed groups from Mindanao, in the southern part of the Philippines.
  
Some Filipino media reports suggested that at least some of the men who crossed the waters to Sabah are MNLF fighters. But that has not been confirmed.
  
The MNLF signed a peace deal with the Manila government in 1996, while the Moro Islamic Liberation Front (MILF), a MNLF splinter, recently forged its own tentative peace agreement with the Filipino government (with the aid of Malaysia).
  
By far the smallest of the three groups, Abu Sayyaf opposes the agreements, as they grant autonomy to parts of Muslim Mindanao, because Abu Sayyaf has said it wants an Islamic state in the southern Philippines.
  
And Abu Sayyaf has been known to make the same crossing to Malaysia as these self-described descendants of the Sultan of Sulu, much more frequently than other groups, as they have been pursued on and off by the Filipino Army.
  
Abu Sayyaf has long been linked to Al Qaeda. It’s known for hosting the likes of Khalid Sheihk Mohammed, a central figure in the 9/11 attacks. And it is also known for taking 20 people, mainly tourists, hostage in 2000 in Malaysia.
  
These days, though, the group seems more like a criminal gang than a politically-motivated terror cell. It is currently holding, by some estimates, six foreign hostages who it likely wants to exchange for ransom, a money-making tactic used by Abu Sayyaf in the past.
  
MNLF leaders spun a recent attack on Abu Sayyaf as an attempt to crush the group, end such hostage-taking, and thus widen the appeal of the impoverished southern Philippines to tourism.
  
If this group of self described descendants are linked to either the MILF or MNLF, Manila will hardly be happy that groups with which it signed peace deals crossed to Malaysia and faced off with Malaysian soldiers. If they're linked to Abu Sayyaf, it would highlight the inability of US-trained Filipino troops to rein in the group.