KAMPALA, Uganda -- Ethiopian security forces have killed more than 400 people in a crackdown on protests in the Oromia region since November, Human Rights Watch said Thursday.

Tens of thousands of others have been arrested, the rights group said in a new report , citing the accounts of 125 protesters, witnesses and others.

The student-led protests were sparked by a government plan to expand the municipal boundaries of the capital, Addis Ababa, into Oromia, where farmers fear they will lose their land. The development proposal has since been retracted.

The security forces used live ammunition for crowd control repeatedly, killing one or more protesters at many of the hundreds of protests over several months, according to Human Rights Watch. Many of those killed were students, including children under 18, the group said.

"Ethiopian security forces have fired on and killed hundreds of students, farmers and other peaceful protesters with blatant disregard for human life," said Leslie Lefkow, deputy Africa director at Human Rights Watch. "The government should immediately free those wrongfully detained, support a credible, independent investigation and hold security force members accountable for abuses."

Ethiopia's government frequently faces allegations of rights abuses against opposition groups, journalists and minority groups.

"It is very difficult for me to respond to every number that is plucked out of thin air," said Ethiopia's communications minister, Getachew Reda. He said the country's parliament has adopted a separate report by the the country's Human Rights Commission that puts the number of people killed during the Oromia protests at 173, with 28 of them either security forces or officials.

Reda acknowledged the report blamed the government on a number of issues but said security forces didn't use disproportionate force.

Meseret reported from Addis Ababa, Ethiopia