(Bloomberg) -- A bombing that killed four people and wounded dozens in southern Philippines early Sunday was “perpetrated by foreign terrorists,” President Ferdinand Marcos Jr. said.

At least 50 were injured in the blast during a Catholic mass at a gymnasium in Mindanao State University in Marawi City, according to the Philippine military. 

The military said tactics used in Sunday’s attack were similar to how the January 2019 explosions in a cathedral that killed at least 20 people in Jolo town in Mindanao, were carried out.

“Security alert is heightened to ensure the safety of our people,” Philippine military spokesman Colonel Medel Aguilar said in a mobile phone message, declining to confirm media reports pointing to Islamic State terrorists taking responsibility for the attack.

In early 2019, suicide bombers carried out the Jolo attack days after voters endorsed a new autonomous Muslim region to end decades of violence in the restive south. In mid-2019, a blast in Sulu province killed five and wounded nine others.

At that time, martial law was still in place in Mindanao two years after clashes between government troops and militants backed by foreign terrorists erupted in Marawi City in 2017. 

Marcos on Sunday urged the public to remain calm as authorities stepped up security.

“I have instructed the Philippine National Police and the Armed Forces of the Philippines to ensure the protection and safety of civilians and the security of affected and vulnerable communities,” Marcos said in the statement. “Additional security personnel are also being deployed.”

“Extremists who wield violence against the innocent will always be regarded as enemies to our society,” Marcos said.

The US condemned “in the strongest terms the horrific terrorist attack” and added it’s in “close contact with our Philippine partners,” according to a State Department statement on Nov. 3.

The five-month fighting in Marawi in 2017 killed more than 1,000 people, displaced tens of thousands and destroyed much of the city that is taking a long time to rebuild.

--With assistance from Ian Fisher.

(Adds background in third paragraph, US statement in ninth paragraph.)

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