MANILA - The Philippine National Police (PNP) denounced a fatal ambush on a police team allegedly launched by the New People’s Army.

“The trademark of ruthless treachery, patented by the CPP-NPA, has reared its ugly head again in this latest attack against a non-tactical police team of laboratory technicians and technical specialists who, by the nature of their functions, are non-combatants,” PNP spokesperson, Senior Supt. Dionardo Carlos said in a statement Wednesday night.

The policemen were reportedly responding to a reported murder in Barangay Sibayan, Bansalan town around 7:40 Wednesday when suspected communist rebels opened fire at their vehicle. Four policemen were killed and another was injured.

There were indications that the victims, who were investigators from the Bansalan Municipal Police Station and the Scene of Crime Operations (SOCO), were able to fire back at their attackers.

"May traces na naka-return fire sila. May mga tama ng bala sa mga puno na pinagtaguan ng mga NPA," Davao del Sur Provincial Director S/Supt. Samuel Gadingan told radio DZMM.

Duterte, who won an election last year on a vow to wipe out illegal drugs, had raised hopes of bringing an end to the communist insurgency that has stunted development for years, especially in central parts of the Philippines.

A ceasefire was declared in August and last month, the government asked the U.S. State Department to remove the rebel movement's Netherlands-based founder and leader, Jose Ma. Sison, from its terrorist blacklist to move negotiations forward.

The peace talks, however, collapsed after both sides traded accusations of truce violations and negotiating in bad faith.