Updated

The United Nations Mission in South Sudan is condemning what it calls "the targeted killings of civilians based on their ethnic origins and nationality" in a contested town.

The mission said Monday that in Bentiu, the capital of oil-producing Unity state, some individuals "associated with the opposition" had used an FM radio station to broadcast hate speech.

The statement said hundreds of civilians were reportedly killed or wounded after rebel forces took control of Bentiu last week.

Toby Lanzer, the U.N.'s top humanitarian official in South Sudan, said in Twitter posts late Sunday that there were shocking scenes of atrocities, with "bodies of people executed" lying in the streets of Bentiu.

Thousands of people have been killed in violence since December, when presidential guards splintered and fought along ethnic lines.