Eritrea says a group of United Nations workers detained by local authorities recently were picked up for "national service."

Eritrea's ambassador the United States, Girma Asmerom, tells VOA that the Eritreans were not arrested, but rounded up to serve in the army, or in a medical or agricultural capacity.

U.N. spokesman Stefane Dujarric tells VOA Eritrea is now holding 11 U.N. staffers - down from the 13 it said were rounded up earlier this week.

The spokesman says the detentions are part of a series of moves by the Eritrean government making it difficult for the U.N. mission there to do its work.

Late last year, Eritrea expelled Western U.N. peacekeepers from its territory and banned U.N. helicopter flights over the country.

Eritrea complains the international community has not done enough to make Ethiopia accept a borderline drawn by an independent panel.