The Rwanda-backed rebels who seized a major city in eastern Congo declared a unilateral ceasefire Monday, citing humanitarian grounds, but there was no sign of them giving up control of Goma at the heart of a region home to trillions of dollars in mineral wealth.

The announcement came shortly after the U.N. health agency said at least 900 people died in last week’s fighting between the M23 rebels and Congolese forces following the rebels’ seizure of Goma, a city of 2 million people.

The rebels were then reported to be advancing on another provincial capital, Bukavu, while vowing to continue to the Congolese capital, Kinshasa, a thousand miles away.

“It must be made clear that we have no intention of capturing Bukavu or other areas. However, we reiterate our commitment to protecting and defending the civilian population and our positions,” M23 rebel spokesman Lawrence Kanyuka said in a statement.