Polling stations have reopened in some parts of Nigeria for a second day of voting after technical glitches disrupted the country's knife-edge presidential election.

The Independent National Electoral Commission (INEC) said 300 of the 150,000 polling stations would accept further ballots after handheld devices to read biometric identity cards malfunctioned.

President Goodluck Jonathan, who is facing a strong challenge from Muhammadu Buhari, was the highest-profile victim of the breakdown on Saturday and eventually had to be registered using the old manual method.

His governing People's Democratic party (PDP) described the situation a "huge national embarrassment" and a vindication of its opposition to the technology, which it said was untested. 

"There should have been a test-run for a smaller election before deploying it for an election of this magnitude," Jonathan's presidential campaign spokesman Femi Fani-Kayode told Agence France-Presse.