Muhammadu Buhari was re-elected Nigeria’s President, results showed Tuesday, after a delayed poll that angered voters and led to claims of rigging and collusion.

Buhari, 76, took an unassailable lead of more than four million votes as the last states were yet to be declared, making it impossible for his nearest rival, Atiku Abubakar, to win.

The win was confirmed as Abubakar won in the very last state to declare — Rivers in the south — but could not claw back the deficit.

Supporters of Buhari’s All Progressives Congress (APC) gathered at his campaign headquarters in the capital, Abuja, to celebrate even before the final results were announced.