"It wasn't a question of taking the life of the head of state, but of spiriting him away, taking him to Spain and forcing him into exile and then of immediately installing the government in exile of Severo Moto Nsa," said the man, introduced as Nick du Toit.
Malabo called on Wednesday for the extradition of Moto, who tried to mount a coup against Obiang in 1997 from Angola and recently set up a government in exile in Spain.
"The leader of this mercenary operation whose aim was to topple the current government had been recruited by the "escapee" from Equatorial Guinean justice Severo Moto Nsa for a sum of $10m," the state radio said.
But Moto denied any involvement in the alleged plot. Severo Moto "has at no time left Spain," said a statement issued by his government in exile.
Moto also went on the offensive, telling Spanish radio station Onda Cero that Obiang was an "authentic cannibal" who "systematically eats his political rivals.
"A while back he paid millions to those they call marabou (sorcerers) to tell him if his power base was safe. They told him that to keep his grip on power he had to kill people close to him.
Wants to eat my testicles
"Obiang wants me to go back to Guinea and eat my testicles. That's clear," he told Onda Cero.
An earlier radio report had described du Toit as a "trafficker in arms and diamonds". It added that the rest of the 15 were from Angola, Armenia, Sao Tome and Principe and South Africa, as well as one German citizen.
But a South African diplomat based in neighbouring Libreville said he had no knowledge of Du Toit's background.
Du Toit said on television: "The group was supposed to start by identifying strategic targets such as the presidency, the military barracks, police posts and the residences of government members."
"Then it was supposed to have vehicles at Malabo airport to transport other mercenaries who were due to arrive from South Africa.
"But at the last minute, I got a call to say that the other group of mercenaries had been arrested in South Africa as they were preparing to leave the country."
An Equatorial Guinean envoy was dispatched to Nigeria on Wednesday for talks with President Olusegun Obasanjo, Nigeria's junior foreign minister Saidu Balarabe Samaila said on Wednesday.
Samaila also confirmed that Nigeria's embassy in Malabo had been surrounded by Equatorial Guinean soldiers with the consent of Nigerian officials, and that around 150 Nigerian citizens had taken shelter there.
Last year when the leader of another oil-rich Gulf of Guinea island nation - President Fradique de Menezes of Sao Tome - was overthrown in a coup, Nigeria took a leading role in returning him to power.