The five - four of them female - were captured outside the main regional city, Port Harcourt. No-one has claimed responsibility for the kidnappings. The number of abductions in the Niger Delta had decreased sharply in recent months following an amnesty deal between the government and militants fighting for more oil money. The abduction of the five, who were volunteering as teachers in poor rural schools, has sparked concern that kidnappings could resume, says the BBC's Fidelis Mbah in Port Harcourt. Many people fear that they will have to step up security again, and night-life in the city will end, he adds. The Niger Delta has been unstable for years since militant groups launched a rebellion to demand that the government spends more of its oil revenue to develop the poverty-stricken region. The militants have carried out a spate of attacks on oil installations and abducted foreigners and locals residents to force the government to agree to their demands. Source: BBC