BAMAKO, Mali — Malians voted Sunday in a runoff presidential election to determine if incumbent Ibrahim Boubacar Keita will remain in office in this West African nation threatened by rising extremist violence.

Keita faced off against opposition leader Soumaila Cisse. Security has deteriorated in Mali since Keita beat Cisse in a second-round election in 2013.

But Keita, 73, is favored to win reelection. He received 41.7 percent of the vote in the first round, in a a field of 24 candidates, and has gained endorsements from some other candidates.

Sunday’s turnout was low amid attacks and threats of violence by Islamic extremists.

The Citizen Observation Pool of Mali, which had more than 2,000 observers, reported several incidents Sunday. It said the chairman of Arkodia village in the north Niafunke commune in Timbuktu region was killed and four election workers were physically harassed.

Two polling stations were burned in Keltamba and election officials were harmed by gunmen in Ngouma commune in central Mali, the group said.

In north and central Mali more than 50 polling stations had closed before noon because of the threats by extremists in those regions.

In the polling centers covered by its observers, the organization said the participation rate was about 8.1 percent. It said 14.4 percent participated in Timbuktu, and only 4.8 percent in Bamako.

However, their observers did not cover all voting areas, and the election commission hasn’t yet given its estimate of voter turnout.

In the July 29 first-round presidential vote, extremists killed three election workers and destroyed some voting materials.

Nearly 43 percent of voters made it to the polls last month and at least 671 polling stations were closed. Despite the relatively low turnout officials called the vote well-conducted.

Malian authorities arrested three jihadists on Friday who said they were preparing to carry out an attack during the vote in Bamako, said Mali army spokesman Colonel Idrissa Traore on Sunday.

Extremists are staging more bold attacks that have spread to central Mali, where both Islamic State and Al Qaeda-linked militants are present. Deadly communal clashes between ethnic groups and accusations of heavy-handed counterterror operations have caused even deeper tensions and mistrust of the state.

Dressed in his traditional white boubou, Keita voted near his home in Bamako on Sunday.

‘‘I hope that everyone will be very vigilant,’’ he said, saying that any suspected attempts at fraud should be reported to police. ‘‘Ultimately this election must end as it should, with the celebration of democracy. . . . This is what we hope for in our hearts.

Cisse, 68, who placed second in the first round with nearly 18 percent of the vote, has blamed Keita for insecurity, violence, and corruption. His opposition party also alleges there was voting fraud in July. Cisse has not received major endorsements from failed candidates but does have the backing of a popular spiritual leader Mohamed Ould Bouye Haidara.

‘‘This time, I have a good feeling,’’ Cisse has said.

Associated Press