Ethiopian Su-27 pilots pose in front of their imposing mounts at Bahir Dar air base.

On Wednesday, Ethiopia's air force said it had shot down a plane transporting weapons for the Tigrayan rebel People's Liberation Front (TPLF) that had encroached on the country's airspace via Sudan, state media reported, without providing details on the date of the operation or the type of the plane.

"The airplane which violated our airspace from Sudan... and aimed to supply weapons to the terror group was shot down by our heroic air force," the Ethiopian News Agency quoted armed forces Maj. Gen. Tesfaye Ayalew as saying.

The news agency said the plane was "believed to be a property of historical enemies who want Ethiopia's weakness and for years have been supporting TPLF."

This comes after fighting between the Tigrayan rebels and government forces erupted in northern Ethiopia for the first time in five months, shattering the "indefinite humanitarian truce" and dealing a blow to hopes for peace talks that would end the 21-month conflict.

The TPLF and the government have both put the blame on each other for the resumption of hostilities.

In the same context, UN Secretary-General Antonio Guterres urged on Wednesday an immediate restoration of a ceasefire in Ethiopia as he expressed shock at the resumption of violence.

"I am deeply shocked and saddened by the news of the resumption of hostilities in Ethiopia," Guterres said. "My strong appeal is for an immediate cessation of hostilities and for the resumption of peace talks."

Since the declaration of the truce at the end of March, the fighting has eased in northern Ethiopia, allowing the resumption of the much-needed international aid convoys to Tigray after a 3-month break.

Ethiopia's northernmost region has suffered significant food shortages and has no access to basic services such as electricity, banking, and communications. Meanwhile, the peace committee said it would submit its peace proposal to the African Union (AU), which has been leading the push to end the war that killed untold numbers of people and kept millions in need of humanitarian aid.

Abiy's government says that any negotiation must be led by the AU's Horn of Africa envoy Olusegun Obasanjo, but the rebels want outgoing Kenyan President Uhuru Kenyatta to mediate.