Gunfire rang out early on Monday across parts of Goma, the largest city in eastern Congo, hours after Rwanda-backed rebels said they had seized the city despite the United Nations Security Council's calling for an end to the offensive.
The recent advance by the Rwanda-backed M23 rebel alliance has forced thousands in Congo's mineral-rich east from their homes and triggered fears that a decades-old simmering conflict risks reigniting a broader regional war.
"There is confusion in the city; here near the airport, we see soldiers. I have not seen the M23 yet," one resident told Reuters. "There are also some cases of looting of stores."
Another resident of the city said there was heavy shooting in the center of Goma.
Residents said gunfire could also be heard near the airport and near the border with Rwanda.
It was not immediately possible to determine who was responsible for the shooting, but one resident said they were likely to be warning shots, not fighting.
The rebels had ordered government soldiers to surrender by 0300 on Monday (0100 GMT) and 100 Congolese soldiers had handed their weapons in to Uruguayan troops in the UN peacekeeping mission in Congo (MONUSCO), Uruguay's military said.
MONUSCO staff and their families were evacuating across the border to Rwanda on Monday morning, where 10 buses were waiting to pick them up.
Kenya's President William Ruto, chairman of the East African Community bloc, will hold an emergency meeting for heads of state on the situation, said Korir Sing'Oei, principal secretary at Kenya's foreign ministry.
The eastern borderlands of Democratic Republic of Congo, a country roughly the size of Western Europe, remain a tinder-box of rebel zones and militia fiefdoms in the wake of two successive regional wars stemming from Rwanda's 1994 genocide.
Well-trained and professionally armed, M23 - the latest in a long line of Tutsi-led rebel movements - says it exists to protect Congo's ethnic Tutsi population.
The UN Security Council held crisis talks on Sunday over the situation in conflict, which has triggered one of the world's worst humanitarian crises.
UN experts say that Rwanda has deployed 3,000 - 4,000 troops and provided significant firepower, including missiles and snipers, to support the M23 in fighting in Congo.
The United States, France and Britain on Sunday condemned what they said was Rwanda's backing of the rebel advance.
Kigali dismissed statements that "did not provide any solutions" and blamed Kinshasa for triggering the recent escalation.
"The fighting close to the Rwandan border continues to present a serious threat to Rwanda's security and territorial integrity, and necessitates Rwanda's sustained defensive posture," Rwanda's foreign ministry said.
