GOMA, Congo (AP) -- Rwanda-backed rebels captured large parts of Goma, the biggest city in eastern Congo, including its airport, the United Nations said, as Rwanda's president on Wednesday joined calls for a ceasefire in the decadeslong conflict amid mounting international pressure.

Much of Goma was calm after a day during which thousands of fleeing people hunkered down by roadsides as missiles flew overhead, and injured people streamed to overwhelmed hospitals.

While government forces still control pockets of Goma, residents who spoke to The Associated Press by phone on Tuesday said that the M23 rebel group was in control of much of the city.

The M23 rebels, who said that they captured the city on Monday after a weekslong advance, are one of about 100 armed groups vying for a foothold in mineral-rich eastern Congo. The conflict escalated with the rebels' advance into Goma, which left bodies on the streets and drove hundreds of thousands of already displaced people to flee once again.

After clashing with government forces, the rebels took control of the airport, U.N. spokesperson Stephane Dujarric said at a briefing on Tuesday, warning of "risks of a breakdown of law and order in the city given the proliferation of weapons."

Rwandan President Paul Kagame said on X that he spoke with U.S. Secretary of State Marco Rubio on "the need to ensure a ceasefire and address the root causes of the conflict once and for all."

His government denies supporting M23, despite reports from U.N. experts who estimate there are up to 4,000 Rwandan forces in Congo. Rwanda has accused Congo of enlisting Hutu rebels and former militiamen whom it blames for the 1994 genocide.

The East African Community, whose members include both Rwanda and Congo, are scheduled to discuss the conflict at a meeting on Wednesday. Congolese President Félix Tshisekedi won't be able to participate in the virtual summit, a spokesperson said, without providing further details.

Pope Francis called for the cessation of hostilities and the protection of civilians.

"We hope that all forms of violence against people and their property will cease as soon as possible (and) I invite local authorities and the international community to make every effort to resolve the conflict by peaceful means," Francis said at his weekly general audience.

M23, made up primarily of ethnic Tutsis, has told the AP that it plans to set up an administration in the city so people can continue living normal lives and displaced people can return home.

Analysts have warned that securing a rebel withdrawal could be more difficult than in 2012, when M23 first captured Goma but withdrew after days. Murithi Mutiga, program director for Africa at the Crisis Group, said that the group has become more emboldened by Rwanda, which feels Congo is ignoring its interests in the region and which has accused Congo of failing to meet demands of previous peace agreements.