The devastating collapse in security has alarmed neighbours such as Indonesia and Malaysia, and defence and army chiefs from the three countries are due to meet in Tarakan on Monday for a ceremony to mark the launch of patrols in the seas between the countries.
Warships from Indonesia, the Philippines and Malaysia held manoeuvres Monday (June 19) in waters plagued by insurgency and banditry off north Borneo, launching coordinated patrols in a region in which Islamic State (IS) influence is growing.
On June 16, some of the Islamist militants who stormed Marawi city in the south of the country in May may have mingled with evacuees to slip away during the battle that has raged for nearly four weeks.
Although a largely maritime-based operation, air and land military assets are also expected to be involved in securing the Sulu Sea, which is located to the north-east of Borneo island and south-west of the Philippines.
BG Padilla was referring to the reported presence in Marawi of foreign fighters, who he said bring a kind of terrorism that is common in the Middle East, but not practiced by local militants. Officials said the fighting has left at least 26 civilians, 257 militants and 62 security forces dead.
Speaking to reporters at the end of the IISS Shangri-La Dialogue on June 4, Dr Ng noted that Singapore had offered to participate in the patrols at any time Indonesia, Malaysia and the Philippines think is appropriate.
Indonesia deployed Sukhoi fighters on June 18 at a base in the northern island of Borneo to strengthen security in case Islamist militants in the Philippines try to flee southwards.
The commander of Tarakan's naval base, First Admiral Ferial Fachroni, told Reuters the other countries would also establish command centres to help in the sharing of information.
The neighbors would not allow Islamic State "to set foot, even just an inch, in our region", he said.
Indonesia's military chief, Gen. Gatot Nurmantyo said Maritime Command Centers have also been opened in the cities of Tawau in Malaysia and Bongao in the Philippines.
The launch was attended by the three countries' defense ministers and marked by an Indonesian navy sail-past and a fly-past of Sukhoi fighter jets.
"We see these (command centres) functioning as a triangle, like a spider's web, where everything inside the triangle will be monitored", said military chief Nurmantyo.