MANILA - President Rodrigo Duterte has reciprocated a ceasefire declaration by communist rebels, his peace adviser said Saturday, after the release of two of their leaders from jail paved the way for the resumption of formal negotiations.

Benito Tiamzon and his wife, Wilma Tiamzon, were freed on bail Friday to participate in five-day-long talks in Oslo, Norway aimed at ending one of the world's longest running insurgencies that has claimed thousands of lives.

The ceasefire will start at midnight Sunday and will last "for as long as necessary to bring peace in the land," Presidential Adviser on the Peace Process Jesus Dureza.

Dureza said the ceasefire would "provide an enabling environment for the success of the peace negotiations."

The Communist Party of the Philippines (CPP) declared the ceasefire after the Tiamzon couple was released. Rebel fighters will observe the truce from 12:01 a.m. on August 21 to 11:59 p.m. on August 27.

The Norway talks, the first formal meeting in a decade, will run from August 22 to 26. Negotiations bogged down under former President Gloria Arroyo after her government refused to release rebel consultants from detention.

The Tiamzon couple was arrested in 2014, under the term of Duterte's immediate predecessor, Benigno "Noynoy" Aquino III. They were among 17 who were granted bail under the current leadership, which has pledged to end the long running communist and Moro insurgencies.

The ceasefire declarations also followed testy exchanged between Duterte and exiled CPP founding chairman Jose Ma Sison. Duterte revoked a unilateral ceasefire that ran for six days in late June after Sison failed to reciprocate it before the President's deadline.