Forces from Ethiopia's northern region of Tigray said on Monday they were pushing south and had recaptured a town from government forces.
Reuters was unable to independently confirm the claim because communication links to the region are down.
Conflict broke out in Tigray eight months ago between central government forces and the region's ruling party, the Tigray People's Liberation Front. The government declared victory three weeks later when it took the regional capital Mekele, but the TPLF kept fighting.
On June 28, the TPLF recaptured Mekele and now controls most of Tigray. But some parts of the west and south are also claimed by the neighbouring Amhara region, which has sent fighters to the contested areas.
TPLF spokesman Getachew Reda told Reuters on Monday that Tigrayan forces controlled Korem, a town 170 kilometres south of Mekele, and were pushing to seize control of the major town of Alamata, 20km further south.
A former resident of Korem now living in the capital Addis Ababa told Reuters a family member fleeing their home reached an area with mobile phone service and confirmed the fighting.
Ethiopian military spokesman Col Getnet Adane did not comment on who was in control of the town but said in a text message "we had declared a ceasefire," referring to a unilateral ceasefire declared by the Ethiopian government after its troops pulled out of Mekele. The TPLF has called the ceasefire "a joke".
A representative for Prime Minister Abiy Ahmed and the head of the government's task force on Tigray did not respond to requests for comment.
Mr Getachew, the TPLF spokesman, said the group wants its prewar borders restored and transport links opened to allow people and humanitarian aid to move.
The conflict has forced nearly two million people to flee their homes and pushed about 400,000 into famine conditions.
On Monday, the World Food Programme said that the first humanitarian convoy to enter Tigray in two weeks had reached Mekele. Major roads into the region have been blocked by government forces and their allies.
Tigray's leaders accuse the central government of blockading the region. Communications and banking have been down since the Tigrayan forces seized Mekele.
The Ethiopian authorities deny blocking aid to Tigray and say they are rebuilding infrastructure.
