Nigeria has at times been considered "Africa's great hope for democracy", an expert told Christian Today, as the first results were announced in the country's hotly contested presidential election.

The electoral commission announced on Monday afternoon that current president Goodluck Jonathan and his closest rival Muhammadu Buhari have each won four states so far. Buhari, a Muslim candidate from northern Nigeria, won by a wide margin in both the key northern swing states of Kaduna and Kano, considered to be the biggest northern battleground state.

Kano is a Buhari stronghold but was seen as one of the northern states where Jonathan had the best chance of making in-roads.

This election is being touted as too close to call, and is the second in which Buhari and Jonathan have gone head to head; they first ran against each other in 2011. Voting finally took place this weekend after a six-week delay over security concerns, though the process has been beset with problems even with better protective measures put in place. Some voters faced hours of delays when new machinery being used to check identities broke down and officials reportedly turned up late, forcing some areas to extend the process into Sunday.

Islamist militants also launched several attacks on voters in the northeast, killing three in Yobe state and 11 in neighbouring Gombe, including an opposition parliamentary candidate. Boko Haram has pledged to derail the elections, having in the past expressed a determination to eradicate Nigerian democracy and replace it with an Islamic state guided by Sharia law.

In addition to Boko Haram's insurgency, one of the main concerns surrounding the election has been that voting may be rigged. The US and UK released a statement today saying that there were "disturbing indications" of political interference in the counting process.

"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."

Hundreds of Buhari's supporters have already begun protesting in Rivers state over allegations that opposition party agents were excluded from a vote-tallying meeting, and there are concerns that violence could break out, despite Buhari and Jonathan both urging supporters to remain peaceful.

Katie Harrison, Tearfund's Head of Communications, told Christian Today that "it's immensely sad and tragic that this is the price some countries pay for democracy".

However, she said the elections so far have proved more peaceful than they would have been had they taken place six weeks ago.

"It would have been even more dangerous, so many people would not have been able to vote, and the level of unrest would have been unacceptable, so it's calmer than it would have been, but still desperately sad," she said. Harrison added that she did not know what intelligence the US and UK had received regarding the process being compromised, but that "they would not have said it unless they really thought it was possible".

"It's certainly one to watch," she said. "If there's any sort of doubt about the veracity of the process it will lead to all sorts of debate about how trustworthy the results are."

In recent weeks, much of the international community has called on Nigeria to ensure that the elections are free and fair. General Secretary of the UN, Ban Ki Moon, and President Obama both encouraged Nigerians to shun violence: "The world's eyes are on Nigeria to make sure these elections are done well," Harrison said.

"It's a powerful nation. It's huge, an economic power, and it's been at various time Africa's great hope for democracy. It's immensely sad that its crisis has compromised progress over the last few years."

The final result of the election is due to be announced on Tuesday.

Additional reporting by Reuters