Six explosions were reported in the Eritrean capital, Asmara, late on Saturday, according to the US State Department.
“At 10.13pm on Nov 28 there were six explosions in Asmara,” the state department said on Twitter, although the cause and location were not clear.
There has been no immediate comment from either Eritrean government officials or Tigrayan forces.
Tigrayan forces fighting Ethiopian soldiers have previously fired rockets at Eritrea.
Earlier on Saturday, Ethiopian Prime Minister Abiy Ahmed announced that federal forces had taken “full control” of Mekelle, Tigray’s capital, within hours of launching an offensive there.
The Tigrayan People’s Liberation Front (TPLF), a political party whose fight against the government began on 4 November, said it was withdrawing from Mekelle.
Thousands of people have fled across the Ethiopian border with Sudan since the fighting erupted in the region.