Police officers investigate at the site of an explosion outside a shopping mall in Cotabato City on the southern island of Mindanao on Monday. Stringer, AFP

MANILA - Residents of Cotabato will likely vote against the southern city's inclusion in a Muslim autonomous area following a deadly New Year's Eve blast, its mayor said Thursday.

Two people were killed and 35 were wounded when a bomb went off outside a shopping mall on Dec. 31. The explosion prompted officers to search the mall, leading to the discovery of another suspected explosive that they destroyed.

The blast came weeks before a plebiscite in January that will determine the scope of the Bangsamoro autonomous region, created as part of peace deal between Manila and the Moro Islamic Liberation Front in 2014.

A commander of the MILF, which wants Cotabato to join the new region, warned in an online video before the blast that "there will be a consequence" for those who will vote against the city's inclusion, said Mayor Cynthia Guiani.

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"He said they're willing to risk everything just to get Cotabato City. That's a threat. It scares the people," she told ANC.

Based on consultations with different sectors, the mayor said her constituents would reject the new region due to the "abuses" from its advocates.

"If you cannot even start a good campaign by being kind to those people you want to vote for 'yes,' then how can you be nice to us when you're already there, when you already have the vote?" she added.

Despite the bombing, Sayadi said authorities will protect the public's right to vote in the plebiscite.

Meanwhile, MILF chairman Al Haj Murad Ebrahim condemned the attack as "an act of cowardice, inhuman, and atrocious."

"We are saddened by the fact that this incident occurred at a time while we are in the thick of preparations for the plebiscite on the ratification of the Bangsamoro Organic Law (BOL) on January 21, 2019," he said in a statement.

Authorities said the main suspect in these blasts was the Bangsamoro Islamic Freedom Fighters (BIFF), a pro-Islamic State armed group that broke away from the MILF.

TROUBLED SOUTH

The southern part of the largely Catholic Philippines has been rocked for decades by violent Muslim separatist insurgent groups including militants linked to IS.

More than 100,000 lives have been claimed by the rebellion, according to a government count.

The region has also suffered from banditry, bloody feuds between powerful clans and communist guerrilla activity.

In September and August, bombs went off in Isulan town, 77 kilometers south of Cotabato, killing at least 3 people.

Martial rule remains in place in Mindanao until the end of 2019 to quell terrorist threats.

President Rodrigo Duterte initially placed Mindanao under military in the wake of the 5-month-long siege by Islamic State-inspired militants on Marawi City in May 2017.

With a report from Agence France-Presse