Jan. 28 (UPI) -- The Islamic State has claimed responsibility for twin bomb attacks on Sunday at a Roman Catholic cathedral in the Philippines that killed at least 27 people.
The claim was issued by the group hours after the attack through its Amaq news agency, The Straits Times reported, citing the SITE Intelligence Group, an American company that monitors terrorist attacks. A formal communique said the attack was carried out by two militants who detonated bombs on their belts.
However, a cellphone discovered inside the church points to the bombs having been detonated remotely, the Manila Bulletin reported.
CCTV footage has authorities zeroing in on homegrown terrorist group Abu Sayyaf, which has ties to IS, ABS-CBN News reported. Col. Gerry Besana, spokesperson for the military's Western Mindanao Command, said the initial probe suggests Abu Sayyaf is responsible.
The National Bureau of Investigation is heading an investigation, Philippine Justice Secretary Menardo Guevarra said Monday.
"It's mass murder and desecration of a place of worship," he said.
Early Sunday, the first explosion occurred in the Cathedral of Our Lady of Mount Carmel before mass -- and the second, an improvised explosive device in the utility box of a motorcycle, ignited in the cathedral's parking lot.
Speculation over who is responsible swirled since the attack occurred in Jolo, an island which lies in the proposed Bangsamoro Muslim-majority autonomous region. Days before the attack, voters overwhelmingly backed a plan to make the region a Muslim autonomous region.
Sulu, which includes Jolo, voted against the Autonomous Region in Muslim Mindanao plan. The military said it is too early to connect the attack with the vote.
Since the attack, Jolo Island has been under lockdown, Philippines Police Chief Director General Oscar Albayalde said.
"The National Headquarters ordered the lockdown. Jolo, Sulu was placed on total lockdown that's why we can see there are no people here and the stores are closed," said Albayalde, the Manila Bulletin reported.