Mali's voters have been warned: Months before Sunday's presidential election, the local branch of al-Qaeda issued a statement telling people in this increasingly volatile West African nation to stay away from the polls.High-profile attacks by a number of extremist groups, including fighters linked to the Islamic State organisation, are complicating what President Ibrahim Boubacar Keita hopes is the path to a second five-year term. Accusations of heavy-handed counterterror operations by Malian security forces and deadly communal clashes between wary ethnic groups add to the insecurity.The 73-year-old Keita, who was elected in 2013 with more than 75% of the vote in the second round, is likely to win again despite competition from 23 candidates."I have hopes of a stable Mali, a peaceful Mali ... headed in the right direction," the president said on Tuesday.His main challenger is 68-year-old Soumaila Cisse, his rival in 2013. The computer science engineer with the Union for Republic and Democracy party has criticised the president for not addressing Mali's rising insecurity.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTER FOLLOW News24 Africa on Twitter and Facebook"He failed to secure us, he failed to give us perspective, IBK failed to preserve our freedoms," Cisse has said, referring to Keita by his initials.Other candidates include 66-year-old Cheick Modibo Diarra, the former prime minister of the transitional government after the 2012 coup. The astrophysicist who also holds US citizenship has worked with NASA, notably on the Mars Pathfinder mission.The 58-year-old Aliou Boubacar Diallo of the ADP-Maliba party is a gold mine-owning businessman who has the support of an influential religious leader, Cherif M'Bouye Haidara. Diallo is popular for advocating the economic reintegration of former jihadists.On Sunday, however, suspected extremists attacked a Diallo campaign team not far from the Mauritanian border.Meanwhile, several political parties have expressed doubts about a valid election after duplicate and fictitious polling stations were listed on the electoral commission's website.The government and the electoral commission have promised a smooth vote, but many among Mali's 8 million registered voters are still worried."If you want to make fraud possible, it is enough for political parties to give money to office agents to corrupt them and they will accept people who come with voter cards that do not belong to them," said Hamadou Guindo, a student in the capital, Bamako. Fraud could lead to post-election violence, he said.Experts say Mali is less secure than in 2013, after French-backed forces pushed extremists in the north from their strongholds. Deadly attacks by extremists have become more brazen in recent months as they take aim at French and Malian forces and a UN peacekeeping mission and move south toward the capital.A more assertive response by Mali's security forces to the attacks has led to accusations by human rights groups of extrajudicial killings, while neighbours turn on each other amid suspicions of joining extremist groups."I am very scared for the elections in my village," said shopkeeper Adama Djiguiba, 39. "There is a great risk that there will be terrorist attacks or inter-communal clashes."Djiguiba lives in Tar in Dogon country in central Mali, which has seen increasing extremist attacks and clashes between ethnic Fulani Muslims and ethnic Dogon.A recent deadly attack in Sevare in central Mali hit the headquarters of a new West African counterterror force. And last weekend rockets were launched at the Sevare airport, though they did not reach their target."The security situation is very fragile, especially lately," said Ibrahim Maiga, a researcher at the Institute for Security Studies. He pointed to clashes days ago between Fulani and ethnic Sogoba in central Mali, along with clashes in the storied city of Timbuktu."I think this situation of insecurity will push the voters not to participate in the vote," Maiga said.