Africa editor, BBC World Service
The US envoy to the Horn of Africa is visiting the Ethiopian capital, Addis Ababa, to press for a peaceful solution to the war in the north of the country.
Jeffrey Feltman’s visit comes as Tigrayan fighters have made some advances towards the capital in recent fighting.
A police spokesman said many supporters of what he described as “illegal terrorists” had been arrested in Addis Ababa.
The US has authorised the voluntary departure of non-essential government employees.
Britain has urged its citizens to leave while commercial options are still available.
Kenya has increased security along its border with Ethiopia.