EU election observers said on Friday that Madagascar's presidential election this week had "very minor" irregularities after candidate Hery Rajaonarimampianina alleged the vote was marred by fraud.
His rival Marc Ravalomanana complained that just six percent of votes had been officially tallied two days after polls closed.
"The irregularities were very minor and won't have any impact on the election's outcome," said the head of the European Union's monitoring mission Cristian Preda.
Two cases of ballot stuffing were reported out of nearly 25,000 polling stations nationwide in Wednesday's vote, he said.
"What we are describing are difficulties and anomalies, which is to say logistical issues that wouldn't have affected the credibility of the elections," Preda told a media briefing in the capital Antananarivo.
But the camp of former president Ravalomanana insisted that slow counting threatened the fairness of the process.
"We are protesting the slow pace of vote counting by the electoral commission," said Ravalomanana campaign director Anisoa Tseheno Rabenja.
"Two days after the vote, we only have six percent of results. But our teams already have (unofficial) results from half of polling stations."
Rabenja also alleged that journalists from the state broadcaster had been bribed to leave the offices of the electoral commission, although his claim could not be independently verified.
"We are warning all the individuals and institutions responsible for managing this election over any attempt to steal it," he added.
African Union (AU) observers called on the three leading contenders, all former presidents, to "show restraint and respect the law".
"It's not in their interests to act in a way that causes tension or trouble," said the AU's observer mission chief Ramtane Lamamra.
Rajaonarimampianina, who ruled from 2014 until September this year when he had to resign to contest the election, said on Thursday that there were "numerous irregularities" in the polls.
"We will not let the people be robbed of their vote," he warned.
Preda, the EU mission chief, said that any irregularities which came to light should be investigated.
"It's important not to cheat. For me, people are attempting to cheat when they make (unfounded) allegations of irregularities, I don't like it," he said.
Lidia Geringer, the head of the European Parliament delegation, described the election as "something of a last chance poll" for Madagascar's democratic and economic development prospects.
Madagascar is one of the world's poorest countries, according to World Bank data, with almost four in five people living in grinding poverty.
The former French colony has struggled to overcome political divisions after a disputed 2001 election that sparked clashes and a 2009 military-backed coup.
The Southern African Development Community regional bloc, which also deployed observers, said that Madagascar had made "improvements to the electoral system" before Wednesday's vote.
"Generally no major incidences of concern were observed," it added.
According to provisional results released by the election commission on Friday, former president Andry Rajoelina was leading the tally of votes counted so far with 42.86 percent.
Fellow ex-president Marc Ravalomanana was close behind with 40.18 percent, according to the results based on 1,350 polling stations out of 24,852.
Rajaonarimampianina trailed on 4.38 percent.
Both Ravalomanana and Rajoelina were banned from contesting the last elections in 2013 under international pressure to avoid a repeat of political violence that engulfed the island in 2009.