MANILA - Police are investigating several "persons of interest" over their alleged involvement in an explosion in Davao City that left 14 people killed and scores others wounded, Mayor Sara Duterte said Saturday.

Duterte, however, declined to give additional details and instead urged Davao City residents to cooperate with authorities who are implementing strict security measures.

"They are pursuing leads and they are pursuing persons of interest. They're following it up with investigation," Duterte told ANC.

"The Davao City Police Office and the Task Force Davao will ensure and will do improvements in their security measures to ensure that no other incident will happen," she added.

The extremist group Abu Sayyaf has claimed responsibility for the attack on a popular night market on Friday that claimed 14 lives and left 67 others injured.

The mayor, the eldest daughter of President Rodrigo Duterte, led some 500 mourners in a mass at the blast site on Saturday.

"Everybody's sad. I think we are more sad than we are afraid because Davaoeños stand up, whatever it is that we face," the mayor said.

Sara Duterte: We will not be terrorized by night market blast