Millions of voters cast ballots in the Democratic Republic of Congo on Sunday, in a widely anticipated election that could mark the African giant's first democratic transfer of power or tip it further into violence.

The election comes after President Joseph Kabila delayed elections for two years after the end of his second and final term, triggering a violent political standoff that left dozens dead across the country.

Read more: Opinion: DR Congo goes to the polls, but Kabila intends to stay on 

Some 40 million registered voters chose from a crowded field of 21 presidential candidates in the election, which took place alongside legislative and municipal ballots.

The opposition has been split between two main candidates, Martin Fayulu, a former Exxon Mobil manager who was a relative unknown months ago, and Felix Tshisekedi, the scion of late opposition icon Etienne. Kabila's preferred successor, the former Interior Minister Emmanuel Ramazani Shadary, ran on the ruling party's ticket.

An opinion poll by the New York University-affiliated Congo Research Group put Fayulu in the lead with 44 percent, followed by Tshisekedi at 24 percent and Shadary lagging behind with 18 percent.

"Today we are writing the end of Kabila, the end of misery for Congolese people," Fayulu said as he cast his ballot in the capital, Kinshasa. "Congo will stop being the laughing stock of the world."

Voting alongside Kabila in the capital, Shadary called for "peace and calm." 

"I am very confident in victory because the Congolese people will trust me, I campaigned all over the country."

Kabila told reporters: "My message today to my compatriots is to come and vote for their candidates and brave the rain."

The opposition has expressed concern that the vote could be stolen and Kabila could rule from the shadows to protect his wealth and network of loyalist power structures. Kabila, in power since his rebel-father-turned-president was assassinated in 2001, is barred from three consecutive terms but has not ruled out another run for office in 2023.

Diplomats and election observers have said that the vast country was poorly prepared for the vote despite repeated delays, raising concerns of a repeat of the violence following elections in 2006 and 2011.

"A Shadary victory is almost certain to be contested by the opposition as illegitimate — but that's nothing new and isn't just due to the problems we are seeing today," Jordan Anderson, an African political risk analyst at IHS Markit, told DW.

"When it comes to Kinshasa and other opposition strongholds, there has been clear potential for post-election protests and violence for some time. But the fact that the elections are actually being held shows that the government believes it can use the security services to contain the resulting civil unrest" in the capital and major cities, he said. 

Credibility of election in question 

Since gaining independence from Belgium in 1960, Congo, despite its wealth of natural resources, has faced coups, despots, assassinations, foreign interventions, civil war and the gutting of state institutions and authority through corruption and patronage networks. Elections are rare — free and fair elections without irregularities non-existent.

The opposition has for months warned that the election would be unfair and illegitimate, citing among other things excluded candidates, confusion or manipulation surrounding new voting machines and lack of an audit of voter rolls.

Just 9 percent of the country has electricity and many people have never used computers, heightening worries over voting machines. 

Some 41,000 election monitors were deployed by the influential Catholic Church for the vote.

Abbe Nshole, secretary general of the Bishops Conference (CENCO), told DW that there were reports of 5,444 problems with voting machines, 115 cases of election observers being blocked from polling stations and another 44 reports of vote buying.

The vote was marked by cases of hundreds of polling stations opening late, long lines, absent voter lists, problematic voting machines and occasional confusion over where to vote, said election observer Dany Singoma, a member of the Civil Society for Continuing Dialogue.

"But on the whole, everything went peacefully," he told DW.

Jean-Pierre Kalamba, a spokesperson for the national election commission (CENI), confirmed similar voting issues but said authorities had addressed them.

"The election takes place. There are minor problems here and there and we solve the problems we are aware of," he told DW, adding that those still waiting in line after polls closed at 5 p.m. local time would still be able to vote. 

A voter named Joseph from the Kingabwa district of Limete municipality in Kinshasa told DW he had arrived at the polling station at six in the morning. 

"We were told that the voting machines were there, but there are no cables or other accessories needed to connect the machines so we can't vote. Now it is 4 p.m. Now we are told that the voters' lists are there, but the cables are still not there. So why are we waiting here, and if the the polling station opens at 4 p.m. - when do you close it again?  At 17:00 poll closing time, or at 20:00 or 21:00, or when?" he said. 

The election's credibility has been strained by repeated delays. A decision by the electoral commission last week to postpone until March the vote in the eastern cities of Beni and Butembo due to an Ebola outbreak bars some 1 million mostly opposition supporters. The eastern Kivu region is home to dozens of armed groups.

On Sunday, more than 10,000 people in Beni staged a self-organized election, vowing to deliver the results to the electoral committee.

One voter taking part in the mock election in Beni told DW that Kabila was trying to take away their vote.

"We want a change at the top of the country. We don't want to wait until March to vote, because the election was already delayed in 2016, then again by a week this month. Too much is too much," he said.  

Anderson, the DR Congo analyst, said the delayed vote in the volatile Kivu region could cause problems for the government.   

"The electoral commission refusing to recognize the results of these polls would clearly stoke local anger, in a part of the country where many people already feel ignored and abandoned by the Kinshasa government," said Anderson.

DW correspondents Wendy Bashi and Saleh Mwanamilongo in Kinshasa, Jacques Vagheni in Goma, John Kanyunyu in Beni, and Rémy Mallet in Bonn, Germany, contributed to this report.