Some people lined the streets to clap and cheer the fighters as they marched and drove into the city centre without resistance. It is the second city after Goma to fall to the rebels in the mineral-rich region in the past few weeks.

The Congolese government has acknowledged its fall and urged residents to stay at home “to avoid being targeted by the occupying forces”.

The UN and European countries have warned that the latest offensive, which has seen hundreds of thousands of people forced from their homes, could spark a wider regional war.

A resident in Bukavu, who asked to remain anonymous because of concerns for her safety, told the BBC on Sunday that most people were still afraid to leave their homes.

“Since yesterday the children and the youth took the weapons. They are shooting everywhere in all directions, they are looting,” she said.

“This morning the M23 entered and they were acclaimed by the people, very happy to see them. We don’t know if it’s because they are afraid or because they found that there were no authorities in the city.

“The place where I live the crackling [gunfire] can still be heard.”

On Friday, the M23 captured Bukavu’s main airport, which is about 30km (18 miles) north of the city – and then began advancing slowly towards the city, which is the capital of South-Kivu province.

The provincial governor, Jean-Jacques Purusi Sadiki, confirmed to the Reuters news agency the fighters were in Bukavu city centre by Sunday morning, adding that Congolese troops had withdrawn to avoid urban fighting.

This left a security vacuum in the city on Saturday with chaotic scenes playing out, including a reported prison break from the central prison.

The UN World Food Programme (WFP) said a warehouse with nearly 7,000 tonnes of food was looted.

The city of around two million people on the southern tip of Lake Kivu borders Rwanda and is an important transit point for the local mineral trade.

Its fall represents an unprecedented expansion of territory for the M23 since their latest insurgency started in late 2021 – and is a blow to the government of President Félix Tshisekedi.

Government spokesman Patrick Muyaya said Rwanda was violating DR Congo’s territorial integrity through expansionist ambitions and human rights abuses.

The Congolese government accuses Rwanda of sowing chaos in the region – as well as having troops on the ground – so it can benefit from its natural resources, something Kigali denies.

President Tshisekedi wants his Rwandan counterpart Paul Kagame to face sanctions over the latest unrest.

But President Kagame has dismissed such threats – and has repeatedly pointed out that Rwanda’s main priority is its security.

He has long been angered by what he sees as the failure of the Congolese authorities to deal with the DR Congo-based FLDR rebel group, which he sees as a danger to Rwanda.

The group is made up of some members of the ethnic Hutu militia accused of involvement in the 1994 genocide in Rwanda when over 100 days around 800,000 people, mainly from the Tutsi ethnic group, were killed.

Troops from the Tusti-led M23 gathered at the Place de l’Indépendance in central Bukavu on Sunday, where one of its commanders, Bernard Byamungu, was filmed chatting to locals and answering their questions in Swahili.

He urged government forces “hiding in houses” to surrender – and accused the withdrawing military of spreading terror by arming local youths who had gone on a looting rampage.

The African Union (AU) – which has been holding a heads of state summit in Ethiopia this weekend – again urged the M23 to disarm.

“We are all very, very concerned about an open regional war,” Reuters quotes the AU’s peace and security commissioner Bankole Adeo as saying.

The bloody conflict in the eastern DRC took a dramatic turn this week when Kigali-backed fighters from the M23 claimed to take control of Goma in North Kivu province before advancing southwards in the direction of Bukavu, the capital of South Kivu.

“We  will continue the march of liberation all the way to Kinshasa,” declared rebel leader Corneille Nangaa on Thursday, four days after the group said it had captured Goma, where fighting left dozens killed and saw surrendering Congolese soldiers being trucked out of the city to an undisclosed location.

On Thursday, M23 fighters were reportedly within striking distance of a strategic military airport in the city of Kavumu, located about 40km (25 miles) north of Bukavu, according to local sources quoted by AFP news agency.

A United Nations spokesperson warned on the same day that the organisation was concerned by “credible reports” that the M23 was “moving rapidly” towards Bukavu, which has a population of two million.

UN experts claim the M23 – one of more than 100 armed groups vying for control in DRC’s east – is backed by some 4,000 soldiers from Rwanda, which Kinshasa says is pillaging valuable resources from the mineral-rich territory.

Rwanda, for its part, says its primary aim is to eradicate fighters linked to the 1994 genocide, accusing the Congolese military of joining forces with ethnic Hutu-led militias bent on slaughtering Tutsis and threatening its neighbour.

The rebel fighters claim they are open to dialogue with the government in Kinshasa. But Congolese Defence Minister Guy Kabombo Muadiamvita rejected talks this week, saying in a video message that plans for any dialogue with the rebels be “burned immediately”.

In response to the fast-moving crisis, leaders of regional bloc the Southern African Development Community (SADC) convened an emergency summit in Zimbabwe’s capital, Harare, on Friday.

The meeting follows soaring tensions between Rwanda’s President Paul Kagame and South Africa’s President Cyril Ramaphosa after the deaths of 13 South African soldiers in DRC’s east.

Rwanda’s Foreign Minister Olivier Nduhungirehe said on Thursday: “We are ready to defend ourselves if we are attacked by a coalition including South African forces.”

Goma  remained largely without electricity and water on Thursday, as the bodies of several alleged government soldiers lay in the streets.

The M23 offensive has heightened an already dire humanitarian crisis in the region, causing food and water shortages and forcing half a million people from their homes this month, according to the International Organization for Migration.

“Millions of people were already displaced by years of conflict in eastern DRC, and humanitarian needs were massive. With the current alarming upsurge in fighting, an already dire situation is rapidly becoming very much worse,” said IOM director general Amy Pope.

Thousands of people have been fleeing “multiple active conflict zones”, the UN refugee agency, UNHCR, said.

The aid agencies said their warehouses with food and medical supplies have been looted as M23 rebels continue to battle to take control of the city.

Anger has been growing over the M23 offensive, and calls for peace talks to end the fighting are mounting.

“Hospitals are overwhelmed. There are currently hundreds of people in hospital, most admitted with gunshot wounds,” the Reuters news agency quoted Adelheid Marschang, the World Health Organization’s emergency response coordinator for the Democratic Republic of Congo, as saying.

The International Committee of the Red Cross (ICRC) said its hospital received more than 100 wounded in just 24 hours, a number it previously received over the course of a month.

It said this had forced its staff to turn the hospital car park into a triage unit.

The use of heavy artillery in densely populated areas is causing severe injuries, particularly among children, it added.

• What’s the fighting in DR Congo all about?

Both the ICRC and the World Food Programme say their warehouses have been looted in recent days.

Reports say at least 17 people have been killed and close to 400 wounded.

On Tuesday, South Africa said that four more of its soldiers, who are in DR Congo as part of peacekeeping efforts, had died as a result of clashes with the M23.

This brings the total number of South African casualties to 13. Malawi and Uruguay have also lost peacekeepers.

South Africa’s President Cyril Ramaphosa on Monday spoke to his Rwandan counterpart Paul Kagame, with the two agreeing on an urgent need for ceasefire and resumption of peace taks

The African Union is also set to host an emergency meeting later on Tuesday.

Late on Monday, DR Congo President Félix Tshisekedi held a meeting with leaders of some state institutions to evaluate the situation in the city.

“Our soldiers and the [pro-government militia] Wazalendo continue to hold certain positions in the city” said Vital Kamerhe, the speaker of the National Assembly after the meeting.

He said the president would address the nation later on the matter, without giving specific details.

Since Friday, Goma has been cut off from electricity and water, and Mr Kamerhe said the government was working hard to restore them to the city.

He said the government was also seeking diplomatic and political solutions to the crisis.

It came as the new US Secretary of State Marco Rubio condemned the M23 attack in a call with Tshisekedi.

In a statement, the US State Department said the Congolese leader agreed on the need to restart peace talks “as soon as possible” with Rwanda, which is accused of backing the rebels.

Mr Rubio also spoke to Kenya’s President William Ruto, agreeing to push forward peace talks. A meeting called by the Kenyan leader between Tshisekedi and Kagame has been scheduled for Wednesday.

The Congolese government has also asked for another meeting of the UN Security Council – demanding that this time it take tough action against Rwanda

During an emergency UN meeting on Sunday, DR Congo demanded sanctions against Rwanda, saying its forces had crossed into its territory in what amounted to a “declaration of war”.

Following the meeting, the UN condemned M23 advances and the “ongoing flagrant disregard for the sovereignty and territorial integrity of the DR Congo”, including the presence of “external forces”.

Rwanda has in the past denied direct support for the M23, but the UN peacekeeping chief Jean-Pierre Lacroix has said there is no doubt its troops were supporting the rebels.

In the capital Kinshasa, angry protesters on Tuesday burned parts of the French embassy, to express discontent over the M23’s offensive.

They stormed the streets, restricting circulation, and burning tyres and disrupting traffic.

Plumes of smoke could be seen billowing as parts of the embassy went up in flames.

Some residents preferred to observe a day of the “dead city”, following a call by civil societies to stay at home in solidarity with Goma.