A government crisis team spokesman, Alfredo Plaza, said the gunmen freed two more hostages on Saturday and agreed to free the remaining captives when they surrender early Sunday.
Armed tribesmen on the southern island of Mindanao, seized 75 people Thursday at a school and several neighboring homes in the town of Prosperidad.
The leader of the hostage-takers, Joebert "Ondo" Perez, demanded that murder charges against his gang be dropped and that police disarm a rival group. He blamed the rival clan, the Tubays, for the murders of six of his siblings.
The southern Philippines is plagued by banditry, tribal feuds, loosely supervised government-armed militias, and Muslim and communist insurgents.
Officials say many former militiamen have turned to banditry and extortion and that the government has made efforts to disarm them. A government official, Cerge Remonde, said Friday that so far more than 1,000 firearms and close to 600,000 rounds of ammunition and explosives have been confiscated or surrendered to authorities.
The kidnapping Thursday came as government forces continued searching for militiamen suspected of involvement in last month's massacre of 57 people in another part of Mindanao.