The development on Tuesday came as Tigrayan forces said they have seized Alamata, the main town in southern Tigray, following the launch of a new offensive two weeks after the federal government declared a unilateral ceasefire in the face of rebel advances.
The text also called for “the swift and verifiable withdrawal of Eritrean troops from the Tigray region”.
The resolution was presented by the European Union, which hailed a unilateral ceasefire declared by Addis Ababa last month and also its participation in a joint investigation into the Tigray situation. But it voiced grave concern at reported widespread abuses in the region in recent months, including mass killings of civilians and rampant sexual violence.
In particular, it highlighted the reported participation of Eritrean troops in serious abuses there, including violations of international law, “exacerbating the conflict”.
For months, both Ethiopia and Eritrea flatly denied the involvement of Eritrean forces in the conflict, but Ethiopian Prime Minister Abiy Ahmed finally admitted their presence in March, and said they would withdraw.
He had accused them of orchestrating attacks on Ethiopian military bases in Tigray, while the TPLF accused the government and its longtime foe, Eritrea, of launching a “coordinated attack” against it.
After eight months of brutal conflict with federal troops, the Tigrayan forces last month swept across large parts of Tigray and retook the regional capital, Mekelle.
Tuesday’s resolution was met with strong resistance from Eritrea, as well as China and Venezuela, which together presented 15 proposed amendments, which were all rejected.
Before the vote, Eritrea’s representative, Adem Osman Idris, slammed the resolution, insisting that his country’s troops had left the region. Ethiopia also categorically rejected the text, saying it interfered with a continuing investigation into the situation in Tigray.
The resolution did welcome Ethiopia’s decision to agree to the joint probe with the UN rights office, and urged the government to ensure the conditions needed for a “full, unhindered and independent investigation” and for attaining accountability for all violations.
Anita Pipan of Slovenia, who presented the resolution on behalf of the EU, insisted the intention was not to interfere with the probe, but said “for the process to be credible, transparency is needed”.
“Given the seriousness of the situation, the international community has the right to be kept informed.”
UN rights chief Michelle Bachelet told the council last month that the joint investigation which had begun in mid-May was expected to conclude its work in August.
“We promised to liberate every square inch of Tigray,” spokesman Getachew Reda told AFP news agency.
“Yesterday (Monday) we launched an offensive in (the southern region of) Raya and were able to absolutely rout federal defence forces and Amhara special forces divisions,” he said.
“We have been able to secure most of southern Tigray including Korem and Alamata (the main town in the area)”.
Getachew said fighting was also taking place in western Tigray, an area where the United States has raised concerns about ethnic cleansing.
He added their fighters were still “in hot pursuit” of pro-government fighters, adding: “We don’t want to give them a chance to regroup.”
The rebel claims could not be independently confirmed because communications were largely down in the area, while an Ethiopian military spokesman did not immediately respond to a request for comment.