ADDIS ABABA, Ethiopia (AP) — Diplomats are calling on Ethiopia ’s federal authorities and their rivals in the northern region of Tigray to agree to a cease-fire as heavy fighting raises growing humanitarian fears.

African Union Commission Chairman Moussa Faki Mahamat expressed “grave concern” in a statement Sunday over the fighting and called for an “immediate, unconditional cease-fire and the resumption of humanitarian services.”

AU-led peace talks were due to take place in South Africa earlier this month, but were postponed because of logistical and technical issues.

The warring parties had said they were ready to participate in the process, even though fighting persists in Tigray.

“The Chairperson urges the Parties to recommit to dialogue as per their agreement to direct talks to be convened in South Africa by a high-level team led by the AU High Representative for the Horn of Africa, and supported by the international community,” Mahamat said in a statement.

The AU statement followed one issued late Saturday by a U.N. spokesman who said Secretary-General Antonio Guterres was “gravely concerned about the escalation of the fighting” and called for an immediate cessation of hostilities.

Fighting resumed between the Tigray forces and the federal troops in August, bringing an end to a cease-fire in place since March that had allowed much-needed aid to enter the region. Fighting has drawn in forces from Eritrea, on the side of Ethiopia’s federal military.

USAID Administrator Samantha Power called on Eritrean forces to withdraw from Tigray and urged the parties to observe a cease-fire, warning in a tweet that up to a 1 million people are “teetering on the edge of famine” in the region.

“The conflict has displaced millions of people, and camps for displaced Ethiopians have also fallen under attack,” said Power, who warned of further bloodshed if Eritrean and Ethiopian federal forces take charge of the camps.

The cease-fire calls came as heavy clashes were reported near the northwestern Tigray town of Shire, where an attack on Friday killed a International Rescue Committee worker who was distributing aid supplies.

European Union foreign policy chief Joseph Borrell said he was “horrified by the reports of continuous violence, including the targeting of civilians in Shire.”

Tigray forces said in a statement that they welcomed the AU’s cease-fire call.

“We are ready to abide by an immediate cessation of hostilities,” the statement said. Ethiopia’s federal government has yet to respond.

Aid distributions are being hampered by a lack of fuel and an ongoing communications blackout in Tigray. The Associated Press reported Saturday that a U.N. team found there were “10 starvation-related deaths” at seven camps for internally displaced people in northwestern Tigray, according to an internal document prepared by a humanitarian agency.

Millions of people in northern Ethiopia, including the neighboring regions of Amhara and Afar, have been uprooted from their homes and tens of thousands of people are believed to have been killed since the conflict broke out in November 2020.