DAKAR, Senegal — Rwanda-backed rebels appeared to be heading toward a third major city in eastern Congo, residents said Tuesday, as international pressure rose over the M23's expansion in a mineral-rich region that’s critical for global technology.

M23 rebels backed by Rwanda took the city of Goma in a bloody battle. This weekend, the group entered the gold-trading center of Bukavu in eastern Congo after government soldiers fled.

Rebel forces have been seen in the center of Bukavu, the second largest city in the eastern Democratic Republic of Congo (DRC), on Sunday, residents told CNN, as the fighters push to expand their foothold in the mineral-rich region.