The Nigeria Civil Society Situation Room says the presidential election held on February 25 cannot be considered credible.
In a statement issued on Friday, the Situation Room said the elections were marred by poor organisation and operational failure.
They asked that the Independent National Electoral Commission (INEC) provide details of the results it collated for the elections.
The group added that Nigerians should remain calm and express their displeasure in a peaceful and democratic way.