Three top Nigerian presidential candidates signed a "peace" deal meant to ease tensions during campaigning for the 2023 election, though the ruling party flag-bearer was absent from the ceremony.
Past presidential ballots in Africa's most populous country have been marred by violence, fraud, court challenges and a rise in ethnic tensions.
Four leading candidates have emerged in a tight race to replace President Muhammadu Buhari, who is stepping down after two terms with Nigeria's economy struggling and insecurity a major challenge for his successor.
The accord, organised by the National Peace Committee, a private initiative of religious, traditional and opinion leaders, urged candidates to focus on issues and steer away from incitement.
"Commitment to a peaceful and issue-based electioneering campaign should resonate beyond" presidential candidates, INEC election commission chairman Mahmood Yakubu said in a statement.
"It is not enough to simply sign the peace accord. What is more important is to abide by its letter and spirit."
Main opposition Peoples Democratic Party or PDP candidate Atiku Abubakar, Labour Party candidate Peter Obi and the New Nigerian Peoples Party's Rabiu Kwankwaso all signed the document in the Abuja ceremony.
Ruling party All Progressive Congress (APC) candidate Bola Ahmed Tinubu, a former Lagos governor, was not at the signing though his vice presidential running mate appeared in his place.
A total of 18 presidential hopefuls are running, including one woman.
Campaigning for the February 25 election and senate and congressional ballots officially started on Wednesday, though the APC has delayed its official launch saying it needed more time to include more "stakeholders".
The state of Africa's largest economy, rife insecurity and opportunities for young Nigerians will be among the major issues during the five-month campaign.
Analysts say the election race will be close with third party candidate Obi challenging the traditional dominance of the ruling APC and main opposition PDP.