MANILA, Philippines - Tribal gunmen holding dozens of people captive in a Philippine jungle were given a firm warning by the government on Saturday as the crisis entered a third day, officials said.

The small group of gunmen raided a school in the Agusan valley region of the southern island of Mindanao on Thursday and took 75 hostages, including children as well as relatives of their leader's local rival.

Twenty-eight hostages, including 18 children were later freed.

"I outlined to them a certain scenario that would happen if they refused to release the remaining hostages," local social worker Josefina Bajade, the chief government negotiator in the crisis, told AFP.

She would not discuss what this scenario would be.

Bajade visited the gunmen's hideout on a mountainous area near here early Saturday to get them to release the remaining captives, but she returned grim-faced.

She said the gunmen refused to release any more hostages. She would not discuss their position further, clarifying only that the government had not set a deadline.

A large government force of about 400 soldiers and police have earlier deployed in the area.

Authorities have identified the gunmen as members of the Manobo tribe, and said they were wanted on charges of murder and other crimes.