The Filipino president Rodrigo Duterte and his security officials are to visit a Catholic cathedral in the southern Philippines where suspected Islamic militants set off bombs that killed at least 20 people and wounded more than 100.
Witnesses said the first blast inside the Jolo cathedral in the provincial capital sent churchgoers, some of them wounded, to stampede out of the main door.
Army troops and police posted outside were rushing in when the second bomb went off about a minute later near the main entrance, causing more deaths and injuries.
The attack occurred in the Sulu provincial capital on Jolo island, where Abu Sayyaf militants have carried out years of bombings, kidnappings and beheadings and have aligned themselves with the Islamic State group.
Mr Duterte is due to meet with some of the survivors and hold a security meeting with military and police officials on Monday.
Police have put forces around the country on heightened alert to prevent similar attacks.
“We will pursue to the ends of the earth the ruthless perpetrators behind this dastardly crime until every killer is brought to justice and put behind bars. The law will give them no mercy,” the president’s office said.
The bombings came nearly a week after minority Muslims in the predominantly Roman Catholic nation endorsed a new autonomous region in the southern Philippines in hopes of ending nearly five decades of a separatist rebellion that has left 150,000 people dead.
Although most Muslim areas approved the autonomy deal, voters in Sulu province, where Jolo is located, rejected it.
The province is home to a rival rebel faction which is opposed to the deal as well as smaller militant cells that are not part of any peace process.
The SITE Intelligence monitoring group said an IS communique claimed the attack was carried out by two of its suicide bombers who wore explosive belts, one detonating inside the church and the other in the parking lot. The claim could not be independently verified.
The fatalities were 15 civilians and five troops, and the wounded were 17 troops, two police, two coastguard and 90 civilians.
The United Nations and others denounced the attack.
In a statement attributed to a spokesman, Secretary-General Antonio Guterres called for the perpetrators to be brought to justice and reiterated the UN’s support for the Philippines’ efforts to fight terrorism and to carry forward a peace process in the Muslim region.