It could affect how authorities deal with tens of thousands of Filipino migrants living in Sabah, including many undocumented workers, if they become perceived as threats to public safety. Any plan to deport them on a large scale, as Malaysia has sometimes attempted, would be a delicate diplomatic issue.
The crisis could also complicate peace talks brokered by Malaysia between Manila and the Moro Islamic Liberation Front, the main Muslim rebel group in the southern Philippines.
Philippine diplomats in Malaysia deployed a team that includes a consul general and a police attache to Lahad Datu and sought access from Malaysian police for the group to help provide assistance to Filipinos who have been wounded and displaced by the violence. They urged jittery Filipino residents in Sabah to stay calm and avoid any action that might complicate the problem.
The Lahad Datu group is led by a brother of Sultan Jamalul Kiram III of the southern Philippine province of Sulu.
In Manila, Jamalul Kiram III told reporters that he was worried the violence in Sabah might spread because many Filipinos, especially followers of his sultanate in the southern Philippine, are upset by the killing of their compatriots in Lahad Datu.
His daughter, Jacel, who is a sultanate princess, called on Filipinos to stay calm but stressed the sultanate would never back down from its struggle to reclaim Sabah.
"This concerns honor above life," she told reporters. "We will not retreat just like that, because we're fighting for something and our struggle is our right and the truth."
Some opposition politicians in the Philippines have used the crisis to snipe at the government of President Benigno Aquino III, prompting an official to appeal to groups seeking to exploit the issue to stay away from "an already tense situation."
"What we would like to remind anyone who is tempted to get involved in this issue for political reasons is that there are actual lives at stake here," presidential spokesman Ricky Carandang said. "It's not just about politics."
Associated Press writer Jim Gomez in Manila, Philippines, contributed to this report.
Cut pounds of stomach fat every week by using this 1 weird old tip.