Nigerian President Olusegun Obasanjo has taken charge of mediation efforts to secure the release of eight foreign oil workers seized Friday.

Presidential spokeswoman Remi Oyo told VOA Saturday that substantial progress has been achieved in negotiations involving President Olusegun Obasanjo and the group responsible for Friday's kidnapping.

"The update is that, negotiations are still going on, and substantial ground has been covered," said Oyo. "President Obasanjo is at this hour optimistic, very optimistic that we will come to a full resolution of the problem, and that the hostages will be released unharmed in the shortest possible time."

Oyo said Friday's abduction was carried out by a local community group seeking to settle scores with an oil company for its alleged refusal to fulfill the terms of an earlier agreement. She said no militants were involved.

"It is a local problem between the community and an oil company that is operating in the area," she said. "So, it is not a case of militancy. It is important that we make the difference that this is not a case of militancy."

The company that operates the oil rig where the hostages were taken has also confirmed reports that the kidnappers have offered to negotiate the release of the hostages - six Britons, an American and a Canadian.

Militants in the Niger Delta have blown up pipelines and kidnapped foreign workers in recent months to press their demands for a greater share of the country's oil wealth.

Other groups and communities have kidnapped oil workers as bargaining chips to force companies to deliver on a wide range of benefits, including employment for local people, and environmental impact and development projects.

Friday's abduction raised new security fears, after a campaign of militant attacks earlier this year on oil facilities in the Delta cut a quarter of crude oil output from Africa's top producing nation.