France and its allies Monday sought to drum up hundreds of millions in aid for Sudan a year since its civil war erupted, sparking one of the world's worst and most underfunded humanitarian crises.

Tens of thousands of people have been killed and 8.5 million more have been forced to flee their homes since fighting broke out on April 15 last year between rival generals.

Sudan is experiencing "one of the worst humanitarian disasters in recent memory", with more people displaced inside the country than anywhere else in the world and a fast-growing hunger crisis, the United Nations says.

At the international conference in Paris, France is seeking contributions from the international community, and attention to a crisis that officials say is being crowded out of the global conversation by ongoing conflicts in Ukraine and Gaza.

"For a year the Sudanese people have been the victims of a terrible war," French Foreign Minister Stephane Sejourne said. Yet they had also suffered from "being forgotten" and "indifference".

"This is the reason for our meetings today: to break the silence surrounding this conflict and mobilise the international community," he said in opening remarks.

The conference, co-hosted by Germany and the European Union, was to include a ministerial meeting on political matters as well as a humanitarian meeting to raise funds for the crisis.

- 'Staggering' indifference -

Aid workers say a year of war has led to a catastrophe, but the world has turned away from the country of 48 million as conflict rages between Sudan's army and the paramilitary Rapid Support Force.

Only five percent of the 3.8-billion-euro ($4.1 billion) target in the UN's latest humanitarian appeal had been funded ahead of the conference this year, according to the French foreign ministry.

At its opening, a total of 840 million euros ($895 million) had been pledged after separate announcements from France, Germany, the European Union and the United States.

A diplomatic source, asking not to be named, said total donations could well top "a billion euros" by the end of the meeting.

On the fifth anniversary of a fire that ravaged the French capital's Notre Dame cathedral, the charity Save the Children contrasted the lack of donations for Sudan with the international response to the Paris blaze.

"It is staggering that after a fire in which nobody died, donors from across the world were so moved to pledge funds to restore Notre Dame," said its country director in Sudan, Arif Noor.

"Meanwhile, children in Sudan are left to fend for themselves as war rages around them, starvation and disease are on the increase and almost the entire country's child population has been out of school for a year."

Fourteen million children need humanitarian assistance to survive, Save the Children says.

Will Carter, Sudan country director for the Norwegian Refugee Council, earlier said civilians in Sudan were "enduring starvation, mass sexual violence, large-scale ethnic killing, and executions".

"Millions more are displaced, and yet the world continues to look the other way."

An estimated 1.8 million people have fled Sudan -- many to neighbouring Chad, now also suffering a humanitarian crisis -- and 6.7 million have been internally displaced.

- 'Better coordination' -

The ministerial meeting, behind closed doors, notably brings together representatives from Sudan's neighbours, as well as from Gulf nations and western powers, including the United States and Britain, along with regional organisations and the United Nations.

German Foreign Minister Annalena Baerbock lamented that mediation efforts so far had failed to stem the conflict.

"We want to work towards better coordination," she said.

Meanwhile, actors from Sudan's civil society, including activists, unionists and journalists, were getting together to discuss "a possible peace process, and what happens after the war", an official said.

Laetitia Bader, at NGO Human Rights Watch, said she hoped that the conference would deliver "a very tough message" to the belligerents, including threats of sanctions.

The warring parties had blocked access for humanitarian assistance, pillaged foreign financial aid and targeted humanitarian workers in attacks, she said.

"This conference is very important, but it should not become an excuse to turn the page and forget about Sudan, again," she added.