ADDIS ABABA, Ethiopia (AP) — Ethiopia says 78 civilians died in last week's unrest that was sparked when a prominent activist said the government had removed his personal security detail.

Prime Minister Abiy Ahmed's spokeswoman said Thursday that 409 people were arrested.

Billene Seyoum described the days of unrest as a "senseless act of violence." Army troops were deployed to restore order.

The activist, Jawar Mohammed, has urged calm. Violence often along ethnic lines is posing the greatest challenge to Abiy, who won this year's Nobel Peace Prize for his sweeping political reforms. Some fear the violence will only increase ahead of Ethiopia's election in May.

"We won't stop the ongoing reforms no matter what. These new challenges indicate how hard and scary the future could be if we don't stand together," Abiy said in a statement on Oct. 26.