Two bombs have exploded outside a Roman Catholic cathedral on a southern Philippine island where Muslim militants are active, killing at least 21 people and injuring more than 70 during a Sunday mass.
The first blast sent people, some of them wounded, running out the church's main door. While police and army troops tried to enter the building, the second blast went off, causing more deaths and injuries.
The Site Intelligence Group, which monitors activities of suspected terror groups, said on its website that the Islamic State's East Asia Province issued a formal communiqué claiming two of its members detonated two suicide explosive vests, one inside the Mt. Carmel Cathedral and another one at the church's parking area.
"The perpetrators of these crimes should be brought to justice and a clear signal given that attacks of religious places of worship will never be tolerated".
Jolo Mayor Kherkar Tan, citing a report from the municipal police, said on Sunday that the explosions killed 25 people and wounded 81 others. Some of the injured were evacuated by air to the nearby city of Zamboanga. "The law will give them no mercy", Philippine President Rodrigo Duterte's office in Manila said.
It added that "the enemies of the state boldly challenged the government's capability to secure the safety of citizens in that region".
"There are high-level law enforcement operations against them (Ajang-Ajang)", said Rommel Banlaoi, chair of the Philippine Institute for Peace, Violence and Terrorism Research.
Although Sulu, including Jolo, was among only a few areas that rejected autonomy, it will still be part of the new entity when it is fully formed in 2022.
Islamic State said previous year it was behind what it called a suicide bombing, when a device was detonated by the driver of a van when he was stopped at a remote checkpoint in Basilan. The province is home to a rival rebel faction that is opposed to the deal as well as smaller militant cells that are not part of any peace process.
The Indonesian government has expressed its condolences following the twin bombing on Jolo Island in the southern Philippines and confirmed that no Indonesians were among the victims.
"With the creation of the Bangsamoro Autonomous Region in Muslim Mindanao (BARMM), the CCA appeals to Christians in the region to be in unity with all peace-loving Muslim and indigenous communities and work together against violent extremism".
The main Islamist militant group is Abu Sayyaf, which has claimed responsibility for numerous horrific terror attacks that have rocked the country in recent times.
They voted for the new region called Bangsamoro, or nation of Moros, in hopes of ending almost five decades of separatist rebellion and reining in a new wave of Islamist extremism sweeping war-torn Mindanao Island.
"It stands for peace in Mindanao", Esperon, a former AFP chief, said.
The bloodshed came less than a week after voters' decisive approval of giving Muslims in the south more control over their own affairs, which sparked hopes of quelling long-time separatist violence.
Marawi, the nation's principal Islamic city, was besieged from May to October 2017 by hundreds of heavily armed local and foreign gunmen who the authorities said aimed to establish a South-east Asian base for ISIS.
"They bravely stayed in Jolo in spite of the threats and insecurities", said the priest.