The Nigeria Delta Liberation Force (NDLF) and the radical Islamist sect Boko Haram are engaged in a war of words over the latter's threats to overthrow the country's president, Goodluck Jonathan.
The move angered the country's Niger Delta militants, who issued a statement defending the president.
The NDLF warned Boko Haram it would immediately avenge any acts that endanger the life of Jonathan, who comes from Bayelsa state in the delta region.
In a statement entitled Boko Haram, Mind Your Utterances, N/Delta Ex-militants Warned, the group's spokesman, Capt Mark Anthony, said the group had been alerted to Boko Haram's threats to bring down Jonathan within three months and would retaliate if his life is threatened in any way.
Another group representing the Ijaw people, who are indigenous to the Bayelsa, Delta, and Rivers States within the delta, also took the president's side and pledged to respond to any attempts to harm the president.
They accused Boko Haram of being a political organisation aimed at overthrowing the president.
"Like other discerning Nigerians, the Ijaw Media Forum knew before now that the entire Boko Haram crisis was a well-organised political movement packaged by those opposed to the Jonathan administration," said a statement by Elder Asu Beks, president of the forum.
The group then threatened to make reprisals, stating:
"That any bomb that explodes within a radius of five kilometres of where the president is at any given time will be matched with a more devastating bombing in any area we consider appropriate to carry out retaliation.
"That the Niger Delta youths agreed to embrace amnesty in the interest of the larger Nigerian nation does not mean that we are pushovers. Enough is enough. Boko Haram has drawn the battle line."