The U.S. Embassy in Addis Ababa has authorised the voluntary departure of some staff and family members as rebel forces in northern Ethiopia make advances towards the capital.
The decision came after the United States said on Wednesday it was "gravely concerned" about the spreading hostilities and called for a halt to military operations in favour of ceasefire talks.
Prime Minister Abiy Ahmed's government has declared a state of emergency, with forces from the northern region of Tigray threatening to push forward to Addis Ababa.
The Tigrayan forces are in the town of Kemise in Amhara state, 325 km (200 miles) from the capital, a spokesman for the Tigray People's Liberation Front (TPLF), Getachew Reda, said late on Wednesday.
The U.S. Embassy said in a statement that further escalation was likely and it was not safe to travel to Ethiopia.
"The (State) Department authorized the voluntary departure of non-emergency U.S. government employees and family members of emergency and non-emergency employees from Ethiopia due to armed conflict, civil unrest, and possible supply shortages," it said.
The government has previously restricted or shut down internet and phone services during civil unrest, it added.
Government spokesperson Legesse Tulu did not immediately respond to requests for comment.
In another sign of international alarm, Uganda announced on Thursday that President Yoweri Museveni has called an East African bloc leaders' meeting on Nov. 16 to discuss the conflict in Ethiopia.
U.N. Secretary-General Antonio Guterres said he had spoken to Abiy on Wednesday "to offer my good offices to create the conditions for a dialogue so the fighting stops".
The U.S. special envoy for the Horn of Africa, Jeffrey Feltman, is expected to arrive in Addis Ababa on Thursday to press for a halt to military operations in the north and to seek the start of ceasefire talks.
On Wednesday, Britain urged its citizens to review their need to stay in Ethiopia and consider leaving while commercial options were available.
The conflict started a year ago when forces loyal to the TPLF, including some soldiers, seized military bases in Tigray. In response, Abiy sent more troops to the northern region.
The TPLF had dominated national politics for nearly three decades but lost much influence when Abiy took office in 2018 following years of anti-government protests.
The TPLF then accused him of centralising power at the expense of Ethiopia's regional states - an accusation Abiy denies.
The Tigrayan forces and their Oromo allies have made significant advances in the past week. Spokesman Getachew on Wednesday pledged to minimise casualties in their drive to take Addis Ababa.
"We don't intend to shoot at civilians and we don't want bloodshed. If possible we would like the process to be peaceful," he said.
A regional analyst, who spoke on condition of anonymity, said the TPLF was likely to hold off on any advance on Addis Ababa until they secured the highway running from neighbouring Djibouti to the capital.
That requires seizing the town of Mille. Getachew said on Tuesday that Tigrayan forces were closing in on Mille.
As the Tigrayan and Oromo forces set their sights on Addis Ababa, Prime Minister Abiy had pledged to bury his government's enemies "with our blood".
However, the statement posted on his Facebook page was removed by the platform for violating its policies against inciting and supporting violence, the company said.