Kidnappers who abducted Seattle missionary
Police and security forces were combing the region in search of Sortor.
Locals in Kogi state, where Sortor was abducted, have been complaining about the high rate of crime and kidnappings for ransom in the region.
The ransom demand suggests that the militant group Boko Haram, which operates farther north in Nigeria and is in retreat after attacks from regional military forces, isn't involved in the crime. Boko Haram has kidnapped hundreds of Nigerian women, and has abducted foreigners, but doesn't normally demand immediate ransoms.
The kidnappers phoned Mathias Emenike, an official of Sortor's Free Methodist Missionary church, on Tuesday to demand a $300,000 ransom, but called back a day later to halve the demand, Nigerian media reported, citing police.
The abductors handed the phone to Sortor, who pleaded with Emenike to raise the funds, according to the reports.
Police expressed confidence that Sortor, kidnapped from Hope Academy in the village of Emiworo late Monday, would be swiftly tracked down and released.
Kogi state police commissioner Adeyemi Ogunjemilusi said police and security forces were working to trace and free Sortor, according to the Associated Press.
"The general concept here is that Americans have money. So they thought that by kidnapping her, they can get money," he said. "We don't think it's a good idea for the family to negotiate with the abductors on the ransom because we are sure we will find her."
She was kidnapped the day after police rescued a local government official kidnapped for ransom in the same state.
Sortor's stepson, Richard Sortor, has said their working-class family cannot afford the ransom.
The kidnapping of wealthy people and foreigners is an industry in Nigeria. Two days before Sortor's abduction, political leaders, academics, businesspeople, retired military officials and women's groups met in Kogi state to protest the high rate of crime in the state.
"We strongly condemn the random assassinations, kidnappings and armed robberies in the area. We are concerned that there has not been effective intervention by the security agents, the Nigeria police in particular, given their constitutional responsibilities," according to a statement from the meeting, signed by Mohammed Aliyu, a retired banker.
It said the law enforcement vacuum was filled by criminals who operated with impunity.