Zamboanga City, Philippines  - One of six schoolteachers seized by Islamic militants in the southern Philippines has died in captivity, a provincial police chief said Saturday.

Senior Superintendent Federico Castro said Noemi Mandi, 34, died six days ago in the lair of Muslim Abu Sayyaf rebels in Basilan province, 900 kilometres south of Manila.

Castro said he received information from a civilian who has access to the Abu Sayyaf hideout that Mandi got sick after she failed to take medicine. She recently underwent surgery to remove a cyst in her ovary, he said.

Mandi and two other teachers were seized on March 13 by Abu Sayyaf rebels off the coast of Naga town in Zamboanga Sibugay province, 990 kilometres south of Manila.

In January, guerrillas also kidnapped three schoolteachers off Zamboanga City.

Aside from the teachers, the rebels in Basilan are also holding captive a 9-year-old boy and a Sri Lankan peace advocate.

Another band of Abu Sayyaf rebels seized three staff members of the International Committee of the Red Cross on nearby Jolo island, 1,000 kilometres south of Manila.

The Red Cross workers - Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Mary Jean Lacaba - had just visited a project at the Sulu provincial jail when they were kidnapped by the rebels on January 15.

The Abu Sayyaf has been blamed for some of the worst terrorist attacks and high-profile kidnappings in the Philippines.

In 2000, it abducted 21 European tourists and Asian workers from a Malaysian resort island and brought them to Jolo. The hostages were ransomed off for millions of dollars before they were freed months later.

The following year, a separate band of Abu Sayyaf rebels seized 17 Filipino vacationers and three US tourists from a western Philippine resort. Most of the hostages were later rescued or ransomed off, but two of the Americans were killed. (dpa)