President Rodrigo Duterte meets with Communist Party of the Philippines leaders Benito and Wilma Tiamzon, and other heads of the National Democratic Front in Malacañang last September. ABS-CBN News

ROME, Italy - The ceasefire between the government and National Democratic Front (NDF) may be in peril as the communist group protested delays in the release of political detainees and alleged military invasion of areas they occupy.

The NDF believes the five-month old truce is "no longer tenable" because it is allegedly being violated by state forces who push communist rebels to withdraw from civilian communities, NDF chief negotiator Fidel Agcaoili said Thursday.

"Iyung aming forces on the ground, nararamdaman na nila na hindi na tenable. Hindi na tenable yung continuation ng ceasefire kasi nga ino-occupy yung mga communities. Pinupupwersa na sila mag-withdraw," Agcaoili told ABS-CBN News just hours before NDF and state negotiators meet for the third round of peace talks in Rome.

(Out forces on the ground feel the ceasefire is no longer tenable because the military keeps occupying our communities. They force communists to withdraw.)

The alleged military advances, he added, violate several agreements signed during peace negotiations from the time of President Corazon Aquino up to the present, including the Joint Agreement on Safety and Immunity Guarantees and Comprehensive Agreement on Respect for Human Rights and International Humanitarian Law (CARHRIHL).

The government also violates the CARHRIHL with the continued imprisonment of almost 400 political detainees, said Agcaoili.

He urged the Duterte administration to prioritize releasing 130 political prisoners affiliated with the leftist movement, who are mostly sick and elderly.

The military and the NDF declared separate unilateral ceasefire in August, paving the way for the first round of talks in August. To guarantee a prolonged truce, the NDF agreed to sign a bilateral ceasefire deal while the government promised to recommend amnesty for political detainees.

'NO VIOLATIONS'

But government peace panel chair and Labor Sec. Silvestre Bello insisted that the Army did not violate its own unilateral ceasefire because "there was no definition of terms" in the first place.

"Wala tayong pinag-usapan na (we did not talk about) what would be considered as a hostile act and what would be considered violation of the ceasefire agreement," he said.

Bello said this is why the government wants a joint ceasefire with the NDF so that "there will be clear definition of terms and conditions including agreement on who will be the referees."

The government, he added, remains committed to freeing political prisoners but their cases should undergo proper judicial process.

Before the resumption of peace negotiations in Oslo in August, four years after the collapse of the last attempt, Duterte allowed 22 rebel leaders to post bail, including senior guerrilla commanders Benito and Wilma Tiamzon.

In November, he also freed four elderly and sick prisoners on humanitarian grounds.

Rebel leaders however immediately demanded the release of 130 more rebels, which Duterte rejected, saying he had made enough concessions and was willing to let peace talks collapse if necessary.

• RELATED STORY: : PH communists warn peace pact unlikely before 2019

-- With reports from Danny Buenafe, ABS-CBN News