MANILA – An improvised bomb caused the explosion at a packed Davao City night market that left 14 people killed and dozens other wounded, the chief of the Philippine National Police said Saturday.

Authorities are looking at two men and two women as “persons of interest” in the attack, which prompted President Rodrigo Duterte to place the entire country under a “state of lawlessness,” said Director General Ronald dela Rosa.

Dela Rosa told a command conference of security officials in Davao City that witnesses linked the four persons to the incident. A police sketch of one of the four has been finished, he said.

"It's not the right time to point fingers. Nalusutan lang talaga [The suspects just slipped past us]," Dela Rosa said of the attack.

Dela Rosa could not immediately confirm the extremist Abu Sayyaf group's claim that it was behind the attack on Friday night.

Davao City Mayor Sara Duterte told ANC earlier Saturday that “persons of interest” have been identified and leads were being pursued. She did not elaborate.

The incident has prompted the government to tighten security in transport terminals as security forces were placed on the highest alert.

Embassies of the United States, United Kingdom and Australia have advised their citizens to either reconsider or avoid travel to the southern Philippines.