Congolese troops have fought back against Rwanda-backed rebels who the U.N. says are moving fast into the South Kivu province after seizing the region’s largest city and an international airport.

Rwandan-backed M23 rebels in Democratic Republic of Congo are seeking to advance south towards Bukavu, the capital of South Kivu province, in an attempt to expand their area of control in the country's east after capturing the city of Goma.

The Tutsi-led rebels have seized Goma, the largest city in east Congo and capital of North Kivu province, which is home to lucrative gold, coltan and tin mines. They then moved on towards Bukavu in South Kivu province,

Rwanda-backed rebels who have captured eastern Congo’s largest city say they plan to take their rebellion to the capital and seek to gain political power.

Rwanda-backed rebels are quickly expanding their presence in eastern DR Congo after capturing Goma, the region's major city, the U.N. said on Friday. View on euronews

Rwanda-backed M23 rebels are moving “rapidly” through South Kivu province toward the city of Bukavu in eastern Democratic Republic of Congo, the United Nations said.

The United Nations expressed deep concern at reports of M23 rebels and Rwandan troops advancing south towards the Congolese city of Bukavu on Thursday, as the militants sought also to assert their control over east Congo's largest city Goma.