Ethiopia and Eritrea have traded blame over fresh clashes in a disputed border region that triggered a bloody war in 1998-2000 and killed thousands of civilians.
Ethiopia said the situation was calm around the border town of Zalambessa on Monday, and government spokesman Getachew Reda alleged that Eritrean soldiers had been "promptly repulsed" by Ethiopian troops.
A resident in the Ethiopian town of Zalambessa, across the border from Tsorona, told Reuters news agency by telephone that he had heard the sound of shelling on Sunday and into Monday morning.
Eritrea disputed this account, saying Ethiopia started the fight.
"The TPLF regime has today, Sunday 12 June 2016, unleashed an attack against Eritrea on the Tsorona Central Front," Eritrea's Information Ministry said in a statement.
"The purpose and ramifications of this attack are not clear," it added.
TPLF refers to Ethiopia's Tigrayan People's Liberation Front, one of the four parties making up the ruling coalition.
Eritrea, which won independence from Ethiopia in 1991, fought a bloody border war with its larger neighbour between 1998 and 2000 which killed about 70,000 people.
Both routinely accuse each other of backing rebels trying to destabilise and topple the other's government, a legacy from the earlier war.
Eritrea, which is under UN sanctions, says world powers have failed to push Ethiopia to accept an international arbitration ruling demarcating the boundary. Ethiopia's government has said it wants talks on implementation.