Filipino armed forces spokesman Col. Arnulfo Burgos Jr. said the ambush, which killed nine people and injured another 12, violated the Comprehensive Agreement on Human Rights and International Humanitarian Law as it victimized non-combatants.
"Despite our openness to the rebels returning to the democratic fold, the NPA rebels continue to wage armed violence, disrupt the peace-building initiatives of the government and even disrespect the peace process," Burgos said.
"Moreover, they continue to capitalize on soft targets, often resolving to inhumane tactics including the use of improvised explosive devices, conduct of ambuscades, extortion activities, and sabotage of vital economic facilities."
Burgos said Filipino troops would follow the rules of engagement and will respect and promote human rights in all operations as they "pursue armed violence that has caused suffering to our people and loss of innocent lives."
Filipino Defense Secretary Voltaire Gazmin said the attack showed the true intentions of the NPA.
"They introduced the true objective of their organization and they do not distinguish soldiers from civilians," Gazmin said in a report by The Philippine Star.
Police reports said those killed were traveling through Barangay Puso, La Castellana, Negros Occidental, when they were attacked about 3:45 a.m. Sunday. The assailants reportedly shouted, "Mabuhay ang NPA (Long live the NPA.)"
In the aftermath of the attack, the military and the police activated Task Force La Castellana to pursue those behind the assault.
Filipino Interior Secretary Manuel Roxas, addressing the 22nd anniversary celebration of the Philippine National Police at Camp Crame, promised the attackers, "We will come after you.
"I say this to all the lawless elements out there: You hit one of us, you hit all of us. We will all come after you."
He said the victims were leaving a village fiesta when they were "mercilessly, brutally, ruthlessly attacked" and that eight of the nine people killed in the ambush were considered "non-combatants."
Underlining the brutality of the attack, Negros Occidental Gov. Alfredo Maranon Jr. stated that the gunmen could be people "high on drugs" and that some of the dead appeared to have been killed with shots to the head.
The Maoist NPA is the armed wing of the Communist Party of the Philippines and was formed in March 1969. It has been conducting a campaign on principle of "protracted people's war," extorting "revolutionary taxes" from business owners in areas it controls.
The CCP refers to the NPA as "the tax enforcement agency of the people's revolutionary government."
The U.S. State Department has designated the NPA Foreign Terrorist Organization, alongside the European Union via its Common Foreign and Security Policy.
Pursuing a conciliatory strategy however, the Filipino government in 2011 has de-listed the NPA as a terrorist organization and undertaken resumed preliminary peace talks with NPA prior to formal negotiations with the CPP.