The postponement by 48 hours of Saturday's polls, hours after voting began in some areas, was a major embarrassment for election commissioner Attahiru Jega, who had promised a break with Nigeria's history of chaotic and flawed elections.

It also raised concern that the 73 million registered voters would lose faith in the credibility of the process, due to continue with presidential elections next Saturday and governorship votes in the 36 states a week later.

Successful elections would be another fillip for foreign investment in sub-Saharan Africa's second biggest economy and strengthen its international standing. Failure could raise questions about how well-entrenched democracy is more than a decade after the end of military rule.

"People are downcast. For once they'd hoped we'd be able to do this thing properly," said community development worker Solomon Gbinigie in the populous Ebute Metta district of Lagos.

"We are encouraging them to come out again tomorrow. It is just embarrassing," he said.

From the sandswept city of Maiduguri near the northeastern borders with Niger and Chad to the mangrove creeks of the Niger Delta in the south, one of the world's largest wetlands, election officials hurried to get everything in place.
Planes ferrying election materials arrived late or not at all ahead of Saturday's vote, causing the postponement.

"We now have all the materials in Port Harcourt and distribution will commence at 12 o'clock. By 11 or 12 tonight we expect materials to be distributed to all areas," said Aniedi Ikoiwak, resident electoral commissioner in Port Harcourt, the main city in the oil-producing Niger Delta.

"By 6 in the morning the materials will be given to the polling officials who will take them to the polling units. Commencement of accreditation by 8 o'clock is guaranteed. Everybody is on duty," he told Reuters.

President Goodluck Jonathan met with the interior minister on Sunday and the government was later expected to declare Monday a public holiday to enable voting to go ahead.

Conspiracy theories abounded on Sunday as to why the elections had been postponed, ranging from a concerted bid by those scared of a free poll to discredit Jega, to an attempt by the ruling party to hang on to power.

A spokesman for ex-military ruler Muhammadu Buhari, Jonathan's main rival in the presidential race, and other opposition officials said they suspected sabotage while some callers to radio phone-in shows urged Jega to resign.

But generally, calmer heads prevailed.