NEW YORK (Reuters) - At lease nine United Nations staff and dependents have been detained in the Ethiopian capital Addis Ababa, a U.N. spokesperson said on Tuesday.

       U.N. security officials have visited the detained staff and the United Nations has asked the Ethiopian foreign ministry to release them immediately, the U.N. spokesperson said in New York.

       The year-long conflict in northern Ethiopia between the government and Tigrayan forces loyal to Tigray People's Liberation Front (TPLF) has intensified in recent weeks. The TPLF and its allies have threatened to march on the capital.

       Ethiopia declared a state of emergency on Nov 2. That proclamation permits the government to arbitrarily arrest, without a court order, anyone suspected of collaborating with a terrorist group. Parliament designated the TPLF as a terrorist group earlier this year.

       Ethiopian government spokesperson Legesse Tulu and foreign affairs ministry spokesperson Dina Mufti did not immediately respond to requests for comment.

       "We are following the arrests of hundreds of Tigrayans in Addis Ababa," Daniel Bekele, head of the state-appointed Ethiopian Human Rights Commission head, told Reuters on Tuesday.

       Addis Ababa police spokesperson said on Monday that the police are only arresting "followers" of the TPLF. "So this is not ethnically motivated at all."

       The U.S. State Department spokesperson said on Monday reports that people of Tigrayan ethnicity were being harrassed are concerning.

       (Reporting by Michelle Nichols,; Additional reporting by Addis Ababa newsroom; Writing by Maggie Fick,; Editing by Franklin Paul)