GENEVA (Reuters) - The United Nations’ human rights chief asked Ethiopia on Thursday to allow monitors into Tigray to investigate reports of killings and sexual violence that may amount to war crimes in the northern region since late 2020. “Victims and survivors of these violations must not be denied their rights to the truth and to justice,” Michelle Bachelet said in a statement, expressing her fear that violations could continue without outside scrutiny. Fighting between Prime Minister Abiy Ahmed’s federal troops and forces of the region’s former ruling party, the Tigray People’s Liberation Front (TPLF), has killed thousands of people, forced hundreds of thousands from their homes and hit infrastructure badly. Until this month, the mountainous region of about 5 million people - with a long history of conflict including war with neighbouring Eritrea - had been off-limits for most media since fighting began in early November. Relief agencies had also struggled for access, while communications were patchy. “Serious violations of international law, possibly amounting to war crimes and crimes against humanity, may have been committed by multiple actors in the conflict,” Bachelet added, mentioning Ethiopia’s army, the TPLF, Eritrea’s military, and troops and militia from the neighbouring Amhara region. Abiy’s government, the Tigray administration, the TPLF, as well as authorities in Amhara and Eritrea, did not immediately respond to requests for comment on the U.N. statement. With witness accounts of atrocities including rape, looting and massacres emerging from refugees and others, the warring sides have been repeatedly blaming each other. Abiy declared victory when the TPLF abandoned the regional capital Mekelle at the end of November. But lower-level fighting has continued in some areas, according to people in Tigray and U.N. assessments. MASSACRES “Deeply distressing reports of sexual and gender-based violence, extrajudicial killings, widespread destruction and looting of public and private property by all parties continue to be shared with us,” Bachelet said. President Isaias Afwerki’s government in Asmara has in the past denied any involvement, while the Abiy administration in Addis Ababa has repeatedly said it is restoring law and order. Abiy’s office said in a statement on Wednesday that it would investigate credible allegations of abuses and bring perpetrators to account. The state-appointed national human rights commission was also investigating and was willing to collaborate with relevant U.N. agencies, it said. Bachelet’s statement said more than 136 rape cases had been reported in hospitals in east Tigray between December and January, with indications of many more unreported. “Reliable sources have shared information about the killing of eight protestors by security forces between 9 and 10 February in Adigrat, Mekelle, Shire and Wukro,” the statement added. Indiscriminate shelling occurred in November in Mekelle, Humera and Adigrat, while mass killings had been reported in Axum and Dengelat, the U.N. rights boss said. Amnesty International last week accused Eritrean forces of killing hundreds of civilians over 24 hours in Axum city last year. Eritrea denied that, but Ethiopia’s rights body also described such killings, though with fewer details, in a rare acknowledgment from the Ethiopian side that Eritrean troops have participated in the conflict. Hundreds of civilians were also massacred in Mai Kadra town early in the fighting last November, rights groups say.