A presumed jihadist killed the head of a polling station in northern Mali when insecurity interrupted a presidential run-off on Sunday, reports the AFP news agency.
Security increased dramatically before the second round of elections between President Ibrahim Boubacar Keita and former Finance Minister Soumaila Cisse. But several polling stations closed in the uneasy central and northern regions due to security problems.
"Jihadists arrived on Sunday around 13:30 (1330 GMT) to a polling station in Arkodia," in the troubled northern region of Timbuktu, a local official told AFP.
"They asked everyone to raise their hands, the president of the polling station tried to escape, the jihadists shot him and killed him," the source said.
The vote on the first round of July 29 was plagued by violence and threats from armed groups that led to the closure of several hundred polling stations, but no victims were reported.
The authorities of the great nation of West Africa said on Saturday that they had interrupted a plan to carry out "selective attacks" in the capital, Bamako, on the eve of the vote.
Sunday's vote in Mali is a repeat of a 2013 showdown between Keita, 73, and Cisse, 68, in the midst of a wave of jihadist bloodshed and ethnic violence.
This year's campaign saw fierce attacks against Keita's perceived failure to stop the violence, as well as growing accusations of electoral fraud.
But the enthusiasm of the public has been low and the opposition is fractured.
"We hope that the new president will do better and know how to compensate for the mistakes of the past," Hajd Aliou Sow, a retired official, told AFP as he left a group of voters early in the morning.
Mali, a landlocked nation that hosts at least 20 ethnic groups where most people live on less than $ 2 per day, has fought against jihadist attacks and intercommunal violence for years.
After the first round of voting, the group of candidates was reduced from 24 to two, since Keita was credited with 42 percent of the votes and Cisse received 18 percent.
Keita cast his ballot in Bamako shortly after 0900 GMT on Sunday and warned against electoral fraud "onstage" after accusations of ballot stuffing and other irregularities.
"How can you organize a fraud when you have the security of your people's support?" Keita said.
Cisse's party told AFP in the early hours of Sunday that the ballots were already circulating, several hours before the polls opened.
The three main candidates of the opposition had launched a last-minute legal challenge to the result of the first round, alleging the filling of the ballot box and other irregularities. But his request was rejected by the Constitutional Court.
Cisse has failed to unite the opposition that backs him, and the challengers in the first round have backed the president or refused to give instructions to vote.
Local observers said voter turnout was low in the afternoon, the West African Network for Peacebuilding (WANEP) said in a statement.
The polling stations closed
The vote will close at 1800 GMT and results are expected within five days. Participation was low in the first round at around 40 percent.
Security had been adjusted for the second round, said an assistant in the prime minister's office, with 20 percent more service soldiers.
But the vote could not take place in several areas, including the northern village of Kiname, 120 kilometers (75 miles) from Timbuktu, where "armed men came and took all the election material to the river bank and set it on fire", a resident told AFP.
"There was no voting in Toguerekotia in the district of Sossobe (in the central region of Mopti) due to insecurity," said WANEP, which has 150 observers across the country, in a statement.
Outside Mali, the hope is that the winner of the elections will strengthen a 2015 agreement that the fragile Sahelian state considers its basis for peace.
The agreement brought together the government, allied government groups and former Tuareg rebels.
But the state of emergency reaches its fourth year in November.
Jihadist violence has spread from the north to the center and south of the vast country and has spread to neighboring Burkina Faso and Niger, often inflaming community conflicts.
France still has 4,500 troops deployed along with the 15,000 UN peacekeepers and a regional G5 Sahel force, with the aim of banishing the jihadists and restoring state authority.