"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.
"Today we have noticed that participation is weak," said Gao prefect Seydou Timbely. "There weren't enough means invested in encouraging the population to come out and vote."
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. The lead suspect in that attack has previous ties to al-Qaida in the Islamic Maghreb.
"The insecurity doesn't give me any fear. 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.
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Associated Press writer Robbie Corey-Boulet contributed to this report from Dakar, Senegal.