The Ethiopian government has expelled six officials from United States organisations helping to prepare for general elections due in six weeks.
They were given 48 hours to leave because they did not have a permit to work and were interfering in local matters, an Ethiopian official said.
One of those expelled said the government was aware of their work.
They were working for the US aid agency, USAids, on voter education ahead of the 15 May poll.
Those expelled, from the International Republican Institute, the National Democratic Institute and IFES, have been in Ethiopia for between one and two months.
One of them, who did not want to use his name, told the BBC's Mohammed Adow as he packed his bags that the government's decision had come as a surprise.
He said they had been working closely with the Ethiopian National Elections board.
"I am very surprised and disappointed because my understanding is that they were all aware of our projects. We had approached the Ethiopian Embassy in Washington months before coming over and we thought that our work here was appreciated," he said.
But a senior official at the ministry of foreign affairs denied his government's knowledge of the presence of the officials and what they were doing.
He said they had started setting up offices in the capital, Addis Ababa without the permission of any government institution.
US embassy spokesman Robert Arbuckle called the expulsion "shocking".
He however said it would not affect the commitment of the US to helping all parties involved in the elections.
Beyene Petros who heads the 14-party opposition coalition United Ethiopian Democratic Forces said the expulsion was "a very bad sign".
He said the government's excuse was "flimsy", because
the officials had gone to help.
Earlier this week, 15 people were arrested for allegedly registering children as young as three years old to vote, polling officials said.
Some 25 million Ethiopians are able to vote in the 15 May parliamentary and regional assembly elections. MPs then choose a prime minister.
Some 35 political parties will contest the polls, although to date the elections have always been won by the ruling Ethiopian People's Revolutionary Democratic Front.