Rebel forces from Ethiopia's northern region of Tigray said they have shot down a military plane and retaken a town from government forces on Sunday.
It comes just a day after the Prime Minister Abiy Ahmed announced the government had taken over the regional capital in the region, Mekelle, and were “fully in control.”
There has not yet been any comment from the government over the claims made by the Tigray People's Liberation Front (TPLF) to the Reuters news agency.
Mr Abiy’s government has been trying to quell a rebellion by the TPLF, a powerful ethnically-based party that dominated the central government from 1991 until Abiy came to power in 2018.
The prime minister has accused Tigrayan leaders of starting hostilities by attacking federal troops. The rebels say his government has marginalised Tigrayans. Tensions spiked over the summer when Mr Abiy announced a delay in the elections, ostensibly due to the pandemic.
Thousands of people are believed to have been killed and nearly 44,000 have fled to Sudan since the fighting began earlier this month.
The conflict has been another test for Abiy, who took office two years ago and is trying to hold together a patchwork of ethnic groups that make up Ethiopia's 115 million people.
Mr Abiy said on Saturday evening federal troops had taken control of the Tigrayan capital within hours of launching an offensive there, laying to rest fears of protracted fighting in the city of 500,000 people.
It was not clear if any TPLF leaders had surrendered or been apprehended since Saturday. Their whereabouts are also unknown.
TPLF leader Debretsion Gebremichael, said on Saturday evening that his forces were withdrawing from around the city but would fight on, raising the spectre of a drawn-out guerrilla war.
On Sunday, he told Reuters that his forces had shot down an Ethiopian military plane and captured the pilot, and had also retaken the town of Axum.
Claims from all sides are difficult to verify since phone and internet links to Tigray have been down and access tightly controlled since the fighting began on November 4.
Also on Sunday, Ethiopian state TV (ETV) said that 70 graves, some individual and some containing multiple bodies were found in the town of Humera in Tigray.
It is not clear at this stage who killed the people in the graves.