Rwandan-backed M23 rebels in eastern Democratic Republic of Congo (DRC) have taken control of the strategic Kavumu airport that serves Bukavu, the region's second biggest city, the rebel alliance and a civil security source said on Friday.

The rebels have been trying to push south towards Bukavu since they seized Goma, the largest city in eastern Congo, at the end of last month.

The capture of Bukavu, the capital of South Kivu province, would represent an unprecedented expansion of territory under the M23's control and deal a further blow to Kinshasa's authority in the east.

"The city of Bukavu can no longer hold," a civil society source in Bukavu said.

Two people who work at the airport, mostly used for NGO and military flights, told Reuters earlier on Friday that it had been effectively closed. Congolese forces had already removed equipment including drones and military aircraft.

A spokesperson for the rebel alliance that includes M23 said in a post on X that the rebels were in control of the airport, and surrounding areas. A member of the civil security service confirmed that to Reuters, while a UN source, a diplomatic source and an M23 source earlier said the rebels had reached the airport.

Congolese President Felix Tshisekedi meanwhile was seeking international support to help end the crisis. He flew to Germany to attend the Munich Security Conference, the presidency said in a statement on social media on Friday. A source at the presidency said he would head to Addis Ababa on Friday evening to attend the African Union summit on Saturday.

The conflict will be high on the agenda at the annual two-day meeting in the Ethiopian capital.

The UN refugee agency voiced concern on Friday at the "rapidly deteriorating" situation, saying the war had left around 350 000 displaced people with no roof over their heads.

GUNFIRE IN KAVUMU

In a video shot in Kavumu by a local resident and seen by Reuters, men in military fatigues are seen walking through town while gunfire can be heard.

Earlier on Friday, rebels seized the town of Katana, 11 km from Kavumu where the airport is located, three sources said.

A video taken by a Katana resident also showed armed men also walking through that town.

"M23 soldiers are blocking the road and are heading towards Kavumu - they already have control of Katana," the resident said.

The town of Kabamba, north of Katana, was taken on Thursday, according to three people.

As the fighting rages in the east, a heavier military presence has also been visible throughout the country's capital Kinshasa, some 1 600 km west of Goma, over the past week, a Reuters reporter said.

After the fall of Goma, protesters in Kinshasa attacked a UN compound and embassies including those of Rwanda, France and the United States, expressing anger at what they said was foreign interference. Looters ransacked the embassy of Kenya.