President Rodrigo Duterte has vowed an impartial investigation into the shootout between agents of the Philippine Drug Enforcement Agency and the Philippine National Police in Quezon City on Wednesday night.

In a televised press briefing on Thursday, Presidential Spokesperson Harry Roque said Duterte expressed both sadness and concern when he was informed of the incident.

"He assured, like the assurance that he made when similar incident happened in Sulu, that we will go again to the bottom of this incident. There will be impartial investigation and justice will be done," he said.

In June last year, four Army intelligence officers died in a shooting incident with PNP personnel in Jolo, Sulu.

Roque said Duterte learned of the incident on Wednesday night when they were almost finished recording the meeting and his "Talk to the People."

Roque said the Palace is confident that with the PNP and the PDEA, which formed an investigation panel, and Justice Secretary Menardo Guevarra's order to the National Bureau of Investigation to conduct its own parallel investigation, "we will know the truth behind this incident and justice will be done."

At least two policemen were killed and four were injured in the shooting near a fast food chain in Quezon City. Celerina Monte/DMS