Abuja (AFP) - Voting in Nigeria's general election was broadly credible despite widespread logistical challenges, domestic and foreign observers said in preliminary findings released on Monday.
Nigeria's Transition Monitoring Group (TMG), set up in the late 1990s to coincide with the end of military rule, said Saturday's election "afforded Nigerians a credible opportunity to exercise their right to vote".
"Late delivery of materials, a slow accreditation process and the inability of card readers to consistently validate voter's fingerprints posed some challenges," TMG said in a preliminary report based on findings from 1,500 polling stations monitored.
But it added: "These issues did not systematically disadvantage any candidate or party."
Political campaigning has been closely run between President Goodluck Jonathan and former military ruler Muhammadu Buhari in what is the first serious opposition challenge in the country's history.
Separately, the African Union praised the conduct of the polls but urged political parties to go to court to resolve any disputes, given fears of violence.
The African Union Election Observation Mission (AUEOM) said the vote was "conducted in a peaceful atmosphere within the framework that satisfactorily meets the continental and regional principles of democratic elections".
Some 1,000 people were killed after Jonathan beat Buhari to the presidency last time round in 2011, when the opposition alleged widespread rigging.
The AU said the election was "generally peaceful during the accreditation as well as voting and counting processes" but said any challenges of the results should not be fought on the streets.
The Washington-based National Democratic Institute (NDI) said "no significant disenfranchisement was observed on election day".
The NDI, which observed 100 polling units, also noted late delivery of materials and various technical glitches but praised the patience and enthusiasm displayed by voters.
The West African bloc known as ECOWAS said on Sunday the elections met the "criteria of being free and transparent", despite "pockets of incidents and logistical challenges".
Nigeria's Independent National Electoral Commission is expected to begin releasing state-by-state presidential results on Monday.
In past elections, some of the most serious incidents of rigging happened during the counting process, rather than on polling day.