Three teachers freed by Filipino militants said they were threatened and slapped during four months of jungle captivity, while the U.S. increased rewards for the capture of leaders of the brutal Al Qaeda-linked guerrillas.

The teachers, working in far-flung southern islands, were abducted Jan. 23 from a boat off Zamboanga city, one of the several ransom kidnappings blamed on Abu Sayyaf guerrillas.

Quizon Freires, Janette Delos Reyes and Rafael Mayonado, who met their parents in tearful reunions and underwent medical checkups Tuesday, said their captors forced them to do chores including gathering firewood and fetching water from a river. If the militants were in a bad mood, they would sometimes hurt the teachers.

"We were often hit in the head or slapped when they were angry. We were often threatened," Freires told reporters.

The kidnappers were demanding $53,000 up to the last minute, but government negotiators stuck to a no-ransom policy, Zamboanga Mayor Celso Lobregat said. He was unaware what prompted the kidnappers to release their captives.

Last week, Abu Sayyaf militants beheaded a kidnapped farm owner in Basilan apparently because his family failed to pay ransom, military officials said.

The militants are still holding at least four hostages, including a Sri Lankan peace activist on Basilan Island and an Italian Red Cross worker on nearby Jolo.

Groups of gunmen stalk potential victims in urban areas, carry out abductions, then hand over the victims to the mountain-based Abu Sayyaf militants, who keep the hostages and negotiate for a ransom, military officials said, citing statements from captured kidnappers.

The Abu Sayyaf, which has about 400 fighters, has been blamed for numerous kidnappings, bombings and beheadings. It is believed to have received funds from Al Qaeda and is on the U.S. list of terrorist organizations.

The U.S. government on Monday increased a reward for the killing or capture of Abu Sayyaf leaders Radullan Sahiron and Abdul Basit Usman to $1 million, as well as $500,000 for Khair Mundos.

The State Department described Usman as a bomb-maker and said that Mundos has worked as a financier for the group.

The State Department added the three to its list of most-wanted terrorists last year.