Gunmen killed more than 100 people in an attack on Wednesday in western Ethiopia, the national human rights body said, the latest in a series of deadly assaults in the area.
The Ethiopian Human Rights Commission (EHRC), a government-affiliated but independent body, said in a statement late on Wednesday that "more than 100 people have been killed in fires and shooting perpetrated by armed men" in the Benishangul-Gumuz region.
The commission said survivors had "disturbing photo evidence" of the attack on sleeping residents in Metekel zone, which began in the early hours of Wednesday and continued until afternoon.
Ethnic violence over land and resources has been a persistent problem in Ethiopia under Prime Minister Abiy Ahmed, often seen as a backlash to the Nobel Peace prize winner's efforts to lead democratic reforms in Africa's second-most populous nation.
Five officials were arrested on suspicion of playing a part in the trouble, the regional government said in a statement without giving further details of possible charges.
At least 36 survivors were being treated for bullet and arrow wounds in a hospital about 90 kilometres (56 miles) from where the attack occurred, the commission said.
"In addition to the damage inflicted on people's lives and bodies, crops have been set alight. One victim told us he saw 18 such fires," the statement said.
There were no security forces in the area at the time, the commission said.
Some of the victims said they knew their assailants, the commission said, adding that humanitarian aid should be sent to assist the displaced and wounded.
The region is home to ethnic Shinasha, Oromo and Amhara, the commission said, the latter two the largest and second largest ethnic minorities, respectively, in Ethiopia.
Some Amhara leaders have asserted ownership of the Metekel zone -- claims that have inflamed tensions with ethnic Gumuz in the area.
- Ethnic attacks -
Abiy visited the Metekel zone on Tuesday and met residents at a town-hall style meeting, posting on Twitter: "The desire by enemies to divide Ethiopia along ethnic & religious lines still exists."
Western Ethiopia has suffered a spate of horrific attacks in recent months.
At least 34 people were slaughtered in an attack on a bus in the same Metekel zone in November.
Twelve others were killed in a separate attack in the zone in October, and 15 died in a similar assault in late September.
In October, Abiy told lawmakers that fighters responsible for those killings were receiving training and shelter in neighbouring Sudan and that Khartoum's assistance was needed to stabilise the area.
Opposition politicians -- notably from the Amhara ethnic group -- have sounded the alarm about what they say is a targeted campaign by ethnic Gumuz militias against ethnic Amhara and Agew living in Metekel.
They claimed at the time that more than 150 civilians had been killed in the attacks, figures that could not be independently verified.
There is no known link between the violence in Benishangul-Gumuz and military operations in northern Tigray region, which have killed thousands, according to the International Crisis Group think tank, and sent more than 50,000 people fleeing over the border into Sudan.