Malians voted Sunday in legislative elections amid heavy security, highlighting fears that a vote seen as the last step in restoring constitutional rule in the battle-scarred country could be sabotaged by rebel attacks. While overall Sunday's vote appeared to be mostly peaceful, sporadic acts of violence served as a reminder of Mali's continued instability. There were also reports of fresh clashes between members of the Tuareg and Peul ethnic groups that left more than a dozen dead, officials said. In the confusion following Mali's March 2012 military coup, rebel groups, including Tuareg separatists and Islamic extremists linked to al-Qaida, took control of northern Mali, prompting France to launch a military intervention in January that largely ousted the militants. But the region has seen an increase in violence in recent weeks, underscoring the persistent challenges in cementing security gains. In Kidal, voters on Sunday were prevented from casting ballots by rock-throwing Tuareg separatists. In Goundam, a desert outpost near the fabled city of Timbuktu, armed men stole at least 10 ballot boxes. And in the region of Gao near the border with Niger, a security official who insisted on anonymity because he was not authorized to speak to the press said 16 ethnic Peul were killed in clashes with Tuaregs that occurred one day before the vote. The official said the violence was believed to be related to the death of an elderly Tuareg man about a week ago at the hands of ethnic Peul trying to rob him. "It's for this reason that armed Tuaregs attacked the Peul in their base near the border with Niger," the official said. Tuaregs are light-skinned whereas the Peul are black. Many Tuaregs have long clamored for an independent nation in northern Mali, claiming that Mali's government, based in the south and dominated by the country's black majority, has marginalized them. Florent Geel, Africa director for the International Federation for Human Rights, also said 16 were killed in Saturday's clashes but added that the organization was waiting on details. He spoke by phone from the capital, Bamako, citing information provided by a member of FIDH in Gao. As voting got underway in Gao Sunday morning, United Nations peacekeepers and Malian soldiers outnumbered voters, though participation increased somewhat closer to midday. The turnout appeared to have fallen short of Mali's peaceful presidential election held in July and August, when Malians elected Ibrahim Boubacar Keita to lead the country in a contest that was decided in a runoff. Several voters said recent insecurity in northern Mali was on their minds, notably the Nov. 2 slaying of two journalists from Radio France Internationale who were reporting in Kidal. To the contrary, it pushes me to come out to vote so we can bring an end to the insecurity," said 26-year-old Aminata Toure, who voted in Gao. Around 6.5 million Malians were eligible to vote in elections for 147 seats contested by more than 1,000 candidates. The European Union deployed more than 100 observers in polling stations throughout much of the country. Mamouni Soumano, a Malian political analyst, said the apparent low turnout would likely benefit the opposition, necessitating runoff elections in much of the country. A runoff vote would be held on Dec. 15. Associated Press writer Robbie Corey-Boulet contributed to this report from Dakar, Senegal.