The United States and Britain said on Monday there were "disturbing indications" of political interference in the counting of votes in Nigeria's election.
"So far, we have seen no evidence of systemic manipulation of the process," US Secretary of State John Kerry and British Foreign Secretary Philip Hammond said in a joint statement.
"But there are disturbing indications that the collation process - where the votes are finally counted - may be subject to deliberate political interference," they added.