An unnamed U.S. source in the area told The Washington Post (NYSE:WPO) that rebels had joined a government faction attempting a coup.

The Justice and Equality Movement, usually known by its initials, JEM, said it was in control of Omdurman, a town across the river from Khartoum, and was using it as a base to oust the government of President Omar Bashir.

"The international community has failed to protect our people, and now we are in a position to do it," said Eltahir Elfaki, a JEM leader currently in exile in Libya. "We are not going to stop until this regime is removed once and for all."

The U.S. source told the Post that several military officers were arrested late Friday and that the rebels, uncharacteristically, appeared to have heavy artillery.