More than 300 residents in the Toboso municipality of Negros island fled their homes on April 19 as gunfire rang out in the remote sugar cane-farming region, the municipal disaster management office told AFP last week.

The number of people killed in the firefight, in which only one soldier was wounded, sparked calls for an investigation.

The two Americans, identified as Lyle Prijoles and Kai Dana-Rene Sorem, arrived in Negros Occidental province about a month before they were killed, the task force said in a statement late Saturday.

"The National Task Force to End Local Communist Armed Conflict (NTF-ELCAC) notes with serious concern the confirmation that a second American national was among those killed in the April 19, 2026 armed encounter," the statement said.

"This brings to two (2) the number of US citizens... who died in the same incident," it added, identifying all 19 killed as "combatant" members of the New People's Army (NPA), which has been fighting a long-running insurgency for nearly 60 years.

Prijoles' name had been released shortly after the clash.

The US Embassy did not immediately respond to a request for comment.

- 'Not a massacre' -

"The military operations carried out by the Philippine Army's 79th Infantry Battalion ... warrant an urgent investigation," Congresswoman Leila de Lima said Saturday.

She pointed to the deaths of a young student and a community journalist in the raid.

In a separate statement, local rights monitor Karapatan said the "sheer number of those killed triggers significant questions and conclusions on the conduct of the AFP (Armed Forces of the Philippines) operations".

The Philippine military, which handed out medals to a number of soldiers involved, said the raid was "a legitimate armed encounter, not a massacre", noting the seizure of 24 firearms.

Addressing a probe launched by the country's Commission on Human Rights, Philippine Army spokesman Colonel Louie Dema-ala told reporters on Sunday the military was "open to investigation and the evidence will speak for us".

The military told AFP last week it had been fighting "remnants" of the NPA near the Toboso municipality.

Dema-ala said the area was "one of the more active remnants of the (guerrilla) front in the central Philippines".

The military estimates the rebel group has fewer than 2,000 armed members left.