Niger Delta kidnappers have freed two of the 11 governing officials seized in Ondo State at the weekend in a row over payments for alleged vote-rigging.
The militants say the Ondo state governor, Dr Olusegun Agagu, reneged on an agreement to pay them for helping rig the April election.
The kidnappers are demanding a ransom of nearly $4m.
But a People's Democratic Party (PDP) official denied the polls were rigged, and said the gunmen would get nothing.
The release of two hostages came after the intervention of Kingsley Kuku, a former member of the Ondo State assembly and secretary of the peace and reconciliation committee.
The militants claim to be members of the Movement for the Emancipation of Niger Delta (MEND), the group blamed for regular hostage-taking in the region as part of their campaign for a larger share of Nigeria's oil money to be allocated to the peoples of the Delta.
Delta militants have carried out a series of attacks and abductions
More than 200 expatriate oil workers have been kidnapped since early 2006 but nearly all were released unharmed in exchange for a ransom.
In the past few months, two young children, an 11-year-old and a politician's mother have been among the Nigerians kidnapped.