The economic, cultural and historical links between Sabah and the nearby Philippines islands, as well as the porous nature of the border between the two, means that many of the sultanate's followers have friends and relatives in Lahad Datu.
And the historical connection still fuels tensions between Malaysia and the Philippines, with Manila retaining a "dormant claim" to Sabah through the Sultanate of Sulu, according to the CIA World Factbook.
The Philippines claims much of the eastern part of Sabah, which was leased to the British North Borneo Company in 1878 by the Sultanate of Sulu. In 1963, Britain transferred Sabah to Malaysia, a move that the sultanate claimed was a breach of the 1878 deal.
Malaysia still pays a token rent to the sultanate for the lease of Sabah.