"An armed group of 50 raided the jail, freeing 23 detainees, ... The armed men who planned the jailbreak were members of the Maute group, which is a Muslim gang in Mindanao that was previously seen carrying Islamic State flags and bandanas, according to the military. ... In the past, the Maute group was involved in bombings and kidnappings. One of its latest attacks was on the Mindanao town of Butig in February. ... Jailbreaks are fairly common in poorly secured Philippine jails. One of the most notorious escapes took place in 2009 when over 100 armed men stormed the prison in the southern island of Basilan, freeing 31 inmates."
https://www.rt.com/news/357495-philippines-muslim-extremists-jailbreak/