The Ethiopian Human Rights Commission has catalogued a litany of abuses, including torture, gang rape and enforced disappearances, saying some may amount to war crimes.
At least 750 civilians caught up in the war have been killed or executed in Ethiopia's Amhara and Afar regions, the country's rights body has said.
The Ethiopian Human Rights Commission (EHRC) has also catalogued a litany of abuses, saying some may amount to war crimes and crimes against humanity.
An EHRC report on Friday said at least 403 civilians had died and another 309 were injured in air raids, drone strikes and heavy artillery fire in the second half of 2021.
The rebel Tigray People's Liberation Front (TPLF) launched an offensive into Afar and Amhara in July.
At least 346 civilians also lost their lives in extrajudicial killings carried out by the warring parties, mainly Tigrayan rebels but also government forces and allied militias, it said.
The rights body also accused Tigrayan rebels of widespread abuses such as gang rape, torture, looting and destroying hospitals and schools in the two regions.
"Tigray forces engaged in abductions and enforced disappearances in a manner that may constitute war crimes and crimes against humanity," the state-affiliated independent body said.
It also accused federal and local security forces in Amhara and Afar of widespread arbitrary detentions.
More than 2,400 health facilities including hospitals in the two regions had ceased operation. Over 1,000 schools were destroyed and another 3,220 damaged, it said.
Friday's report follows a joint investigation by the UN and the EHRC covering November 2020 to June 2021.
It detailed a vast array of rights abuses, mostly blamed on Ethiopian forces and Eritrean troops, who provided military support to Addis Ababa.
The 16-month conflict in Africa's second most populous country between government forces and Tigrayan rebels has killed thousands of people.
According to the UN, the fighting has also displaced more than two million people, driven hundreds of thousands to the brink of starvation and left more than nine million in need of assistance.
Although the intensity of fighting has eased, UN humanitarian agency OCHA said in a bulletin on Thursday that northern Ethiopia remained "highly tense and unpredictable."