By Hader Glang

ZAMBOANGA CITY, the Philippines

The Philippines’ military has confirmed that four suspected rebels were killed a day before ceasefires declared by the government and communist groups go into effect ahead of the resumption of peace talks next week.

Army spokesman Col. Benjamin Hao said soldiers were conducting a patrol following reports of alleged extortion by the New People's Army (NPA) when a firefight occurred Saturday morning in southern Agusan del Sur province.

He was quoted by the Sun.Star news website as saying that the clash broke out after rebels fired on the government troops in San Luis town.

Troops reportedly recovered the bodies of the slain rebels, three AK47 and two M16 rifles, and “rebel documents” at the site.

The clash occurred before ceasefires declared by President Rodrigo Duterte and the Communist Party of the Philippines’ (CPP) -- of which the NPA is the armed wing -- are set to go into effect after 12 a.m. Sunday (1600GMT Saturday).

The government’s ceasefire was announced by Presidential Adviser on the Peace Process Jesus Dureza before he flew to the Norwegian capital Oslo for negotiations Aug. 22-26.

The CPP and NPA had made their declaration Friday after a regional court temporarily released a couple, Benito and Wilma Tiamzon, accused of being leaders of the groups, bringing the number of those released to participate in negotiations to at least 19.

During the talks, the CPP seeks to address a proposal for Duterte to grant a general amnesty for the release of all political prisoners.

More than 500 members of the communist groups, which have been waging a decades-old insurgency, are currently in detention.

Duterte had declared a unilateral government ceasefire during his first state of the union address July 25, only to call it off days later after an ambush by NPA members killed a government militiaman in southern Davao del Norte province.

Previous negotiations with the CPP and its political arm the National Democratic Front collapsed in 2004 after the communists withdrew from the negotiating table on account of the renewed inclusion of CPP founder Jose Maria Sison and the NPA on the United States terrorist list.

In 2014, negotiations again failed because previous President Benigno Aquino III turned down the rebels' demand to release detained comrades -- accusing the rebels of insincerity in efforts to achieve a political settlement.

In his peace overtures, Duterte -- who won the May 9 election -- has said that he will release all political prisoners if party leaders return from exile and sit down for negotiations.

He has also offered the CPP posts in his new government to smooth the way.

The insurgency, waged since March 1969, has claimed more than 3,000 lives over the past eight years, according to the military.

The military estimates that the number of NPA members has dropped from a peak of 26,000 in the 1980s to less than 4,000.