Ethiopia has accused neighbouring Eritrea of carrying out mass kidnappings of Ethiopian civilians along their shared border.
Ethiopia's Prime Minister Meles Zenawi told parliament that the Eritrean government had kidnapped more than 100 Ethiopians working in goldmines in the Northern Tigrai region.
Ethiopia accused its neighbour of leading a series of acts of aggression by orchestrating cross-border attacks and targeting Western tourists.
It routinely accuses Asmara (the capital city of Eritrea) of supporting Ethiopian separatist groups, accusations that Eritrea rejects.
"They recently kidnapped more than 100 young miners who were mining gold in our northwest. And in the northeast, they killed tourists and kidnapped others," Meles said. A group of Western tourists was kidnapped in the Afar region in January.
"We have taken proportional measures in both locations," he warned.
Members of the Eritrea-based Afar separatist group (ARDUF) were responsible for the attack that killed five people from Germany, Hungary and Austria.
The armed insurgents also kidnapped two Germans and two Ethiopians. The Germans were released but the fate of the Ethiopian hostages remains unclear.
Ethiopia retaliated by sending troops into Eritrea, its first military incursion since the two countries ended their 1998-2000 war.
Eritrea accused the US of backing Ethiopia's military operations and called on the UN Security Council to intervene.
"The military incursions were plotted by Washington with the aim of diverting attention from implementing the boundary commission's decision," President Isaias Afewerki said.
Meles said that Eritrea had repeatedly refused Ethiopian peace proposals and pointed to sanctions levelled against it by the UN and African Union. He said Ethiopia had no intention of scaling back military operations.
"It has become the modus operandi of Ethiopia to blame everything on Eritrea," Girma Asmerom, Eritrea's ambassador to the African Union, told Bloomberg.
"They think by lying and lying, the lies may be perceived to be true."
Unresolved border dispute
The war between the two countries claimed the lives of at least 80,000 people and the border dispute that triggered the conflict is still unresolved.
About 1.4 million Afars live in Ethiopia and in smaller numbers in Eritrea and Djibouti.
ARDUF is one of the most prominent rebel groups operating in the region. It was formed in 1993 and seeks the creation of an independent Afar region across Ethiopia, Djibouti and Eritrea.
Analysts have warned that a full-fledged conflict between the two states would have devastating consequences in the region. The Horn of Africa is already gripped by conflicts in Somalia, and between Sudan and South Sudan.