After weeks of negotiations and several deadlines for the group to withdraw, the killing of local policemen prompted Malaysian security forces to flush out the militants with a military operation.

In 2019, eight of these Sulu heirs, who insisted they were not involved in the standoff, hired lawyers to pursue legal action based on the original commercial deal.

However, all attempts by the purported Sulu heirs were ultimately defeated by the Malaysian government and the seizure order was quashed by the courts in all four aforementioned European countries by November 2024.

In response, Jamalul Kiram III, claiming to be Sulu's legitimate heir, decreed on 11 November 2012 that a civilian and military contingent should assert his territorial rights in North Borneo.

[15][50] Months later on 11 February 2013, Agbimuddin Kiram and at least 101 followers arrived in the village of Tanduo, located near Tungku in Lahad Datu from neighbouring Simunul island, Tawi-Tawi, in the southern Philippines.

[54][56] Aquino's statement was supported by Senator Francis Pangilinan, who said: This standoff has reached a critical point where the Philippine government must now act decisively and do what is necessary to protect the general interest of the Filipino people.

Kiram III asked Malaysia to "sit down in a square table and to diplomatically settle the issue on the claim" stressing the need to "come up with a win-win solution".

She expressed disappointment at the apparent lack of support from the Philippine government, adding that Manila needed to balance diplomatic relations and the interests of its constituents.

[59] On 7 March 2013, the Malaysian Foreign Ministry issued a statement that said it considered Kiram's III forces as a group of terrorists "following their atrocities and brutalities committed in the killing of Malaysia's security personnel".

[70] On 2 March 2013, a group of 10 armed men were spotted near Kunak, a district between Lahad Datu and Semporna, according to Royal Malaysia Police Inspector-General Ismail Omar.

[71] The Malaysian government doubled the number of police and army officers, deploying members of the Royal Malay Regiment, in areas where the sultanate's armed supporters were believed to be present.

[75] Idjirani, the secretary-general of Sultan Kiram III, said the violence started when Malaysian policemen, while pretending to round up undocumented Filipinos, shot Imam Maas and his four sons.

[85] At around 11:00am in a Kuala Lumpur rally, Prime Minister Najib Razak delivered the following speech:[84][86][87] I wish to inform you about the latest news that, at around 10am just now, Malaysian security forces has launched a large-scale operation to crush the intruders at Lahad Datu.

I wish to address that, at the initial stage, our only intention is to avoid spilling even single drop of blood on the soil of Sabah, whether amongst the people of Malaysia, or amongst the group that has intruded into our country.

However, I feel deeply disappointed when our good will and sincere intention was responded with acts of shooting and killing, in an extremely cruel manner, against our police forces.

[108] Chua's allegations were met with an outcry by the Malaysian public; citizens and personalities such as Ambiga Sreenevasan and Saifuddin Abdullah called for both parties to forge a bi-partisan consensus to settle the issue.

On the eve of its 2013 general election, Filipino senatorial candidates from the opposition blamed President Aquino for sending unclear messages to the Kiram family.

[118] A report on News5 claimed that some Moro National Liberation Front (MNLF) members were undergoing training in Jolo, Sulu for a rescue mission for abused Filipinos in Sabah.

[8][123][124] On 6 August 2013, the Kota Kinabalu High Court convicted Corporal Hassan Ali Basari, a Malaysian Special Branch officer, of intentionally withholding information about the intrusion of Sulu gunmen at Lahad Datu between January and March 2013.

[126][127] In 2013 during the ensuing conflict, Malaysian authorities announced that deceased militants would be buried in the state if their bodies were not claimed by their relatives, in compliance with the Geneva Conventions.

Justice Stephen Chung made the ruling after finding that the prosecution had succeeded in establishing a prima facie case against them: 16 Filipinos (including one woman) and three local men.

Nine of the 16 Filipinos: Atik Hussin Abu Bakar, Basad H. Manuel, Ismail Yasin, Virgilio Nemar Patulada, Mohammad Alam Patulada, Salib Akhmad Emali, Al Wazir Osman, Abdul, Tani Lahaddahi, Julham Rashid and Datu Amir Bahar Hushin Kiram were alleged to have waged war against the King, a capital offence.

[138] Six Filipinos, Lin Mad Salleh, Holland Kalbi, Habil Suhaili, Timhar Hadir, Aiman Radie and a Malaysian man, Abdul Hadi Mawan were accused of being a member in a terrorist group, which was punishable with life imprisonment and fine.

The sole Filipina Norhaida Ibnahi was ordered to enter her defence for allegedly wilfully harbouring individuals she knew to be members of a terrorist group, which was punishable with 20 years to life imprisonment and fine, or both.

The new charge was made after Justice Chung found the prosecution had shown evidence that they had solicited or given support to a terrorist group, punishable with life imprisonment or a fine.

[143] On 25 July 2016, the court found that nine Filipino militants who led the intrusion could face the death penalty:[144] Atik Hussin Abu Bakar, Basad H. Manuel, Ismail Yasin, Virgilio Nemar Patulada, Mohammad Alam Patulada, Salib Akhmad Emali, Al Wazir Osman, Tani Lahaddahi, Julham Rashid and Datu Amir Bahar Hushin Kiram.

[151] On 22 April 2014, a 57-year-old man in Lahad Datu who claimed to have been given the power to manage the Suluk people in Sabah was arrested for displaying the Sulu Sultanate flag at his home.

This [locals] have played a part in the intrusion in the east coast of Sabah, abductions and cross border crimes prior to the establishment of ESSCOM and ESSZONE.

[171] Izzah claimed that she and Tian Chua were invited to meet with stakeholders from the Philippines, adding that they also met other Filipino politicians such as Hermilando Mandanas and Regina Reyes.

[177] On 22 November 2015, Izzah filed a defamation lawsuit against Malaysian Inspector Police Chief Khalid Abu Bakar and Rural and Regional Development Minister Ismail Sabri Yaakob.