Ethiopia Tuesday claimed Sudanese forces were pushing further into a contested border region, while Khartoum said five Sudanese women and a child were killed in the same area a day earlier.
The two Horn of Africa nations have long feuded over the Al-Fashqa region, where Ethiopian farmers cultivate fertile land claimed by Sudan.
In early December, Sudan accused Ethiopian "forces and militias" of ambushing Sudanese troops along the border, leaving four dead and more than 20 wounded.
Ethiopia, for its part, said last week that Sudan's military had "organised attacks by using heavy machine guns" and that "many civilians have been murdered and wounded".
Dina Mufti, spokesman for Ethiopia's foreign ministry, on Tuesday said Sudanese forces were still advancing into the border region, calling the move an "unacceptable and counterproductive" violation of international law.
"The current situation is the Sudanese force at the border is boosting its position and moving forward... into Ethiopia's hinterland," Dina told a press conference.
He called on Sudan to "return to the previous status quo" to give space for a demarcation process.
"Ethiopia always gives priority to peace and respects international norms. However, Ethiopia has its limit," he said.
Dina has previously accused Sudanese military officers of trying to take advantage of fighting in Ethiopia's northernmost Tigray region to press its territorial claims in Al-Fashqa.
Later Tuesday, Sudan said armed Ethiopians had killed five women and a child in an attack in the same area the previous day.
"This regrettable incident occurred... in the Al-Fashqa region, five kilometres from the border with Ethiopia," Sudan's foreign ministry said.
The women were harvesting crops when the attack took place, the statement added.
"Sudan has condemned in the strongest terms this brutal aggression, and denounced the targeting of defenceless civilians," it said.
The Tigray conflict has spurred tens of thousands of Ethiopian refugees to cross into Sudan.
The two countries share a 1,600-kilometre (nearly 1,000-mile) frontier.
In 1902, a deal to draw up the border was struck between Great Britain, the colonial power in Sudan at the time, and Ethiopia, but it lacked clear demarcation lines.
The two sides held border talks in late December, and Sudan said December 31 that its army had restored control over all border territory that had been taken over by Ethiopian farmers.
The border dispute comes at a sensitive time for ties between the two countries, which are also along with Egypt trying to reach a deal over Ethiopia's massive Grand Ethiopian Renaissance Dam on the Blue Nile River.