Africa's frustration at the UN climate summit boiled over Monday as delegates walked out of key talks and continental giant Nigeria warned the negotiations were now on red alert.

Sources at the marathon talks said Africa led a five-hour boycott of working groups, with the backing of the Group of 77 developing nations, and only returned after securing guarantees that the summit would not sideline talks about the future of the Kyoto Protocol.

The Kyoto Protocol ties rich countries -- but not developing countries -- that have ratified it to legally binding emissions curbs.

It also has an important mechanism enabling the transfer of clean-energy technology to poorer nations.

Yet it does not include the United States, which says the Protocol is unfair as the binding targets do not apply to developing giants that are already huge emitters of greenhouse gases.

Algeria, speaking at a press briefing on behalf of the 53-member African Union, demanded that there should be a special plenary session devoted to Kyoto.

"Otherwise we are going to lose everything," Algeria's chief negotiator Kemal Djemouia told reporters.

Asked about the state of negotiations, Nigeria's pointman rang the alarm bell.

"It is 'climate code red' right now, we are in code red right now, we stand at the crossroads of either hope for Africa or hope dashed in 'Hopenhagen'," Victor Ayodeji Fodeke told AFP.

He said that climate change was already triggering widespread migration in Africa, further increasing the competition for precious resources.

"Look at the situation in Africa," he said.

The Millennium Development Goals will be a mirage, poverty will be further exacerbated. Right now you have climate refugees ... Look at the droughts in east Africa. Climate change is a reality in Africa."

The Nigerian negotiator said that Africa had the support of emerging giants China and India in insisting that Kyoto does not get ignored.

"They are certainly behind us, they are with us that Kyoto must not die."

Yvo de Boer, the UN's climate chief, said there was widespread sympathy for Africa's concerns.

"I think this is not just an African concern," he told a press conference. "The vast majority of countries here want to see an extension of Kyoto."

Scientists say African countries will be in the frontline of climate change this century.

The continent faces greater risk of heatwaves, drought or changed rainfall patterns that could spell misery or malnutrition for millions. Yet it has the slenderest resources of all for coping with these threats.

Activist groups said they fully backed the Africans' stance, arguing that a voluntarist, non-binding approach would deprive the poor of their sole international safety net.

"Africa has pulled the emergency cord to avoid a train crash at the end of the week," said Jeremy Hobbs, executive director of Oxfam International.

"Poor countries want to see an outcome which guarantees sharp emissions reductions yet rich countries are trying to delay discussions on the only mechanism we have to deliver this -- the Kyoto Protocol.

"This is not about blocking the talks, it is about whether rich countries are ready to guarantee action on climate change and the survival of people in Africa and across the world," Hobbs added.

The environmental pressure group WWF said that uncertainty about the future of Kyoto was "creating a lot of mistrust and resentment within these negotiations".

"We believe a continuation of the Kyoto Protocol is a necessary part of the ... outcome of Copenhagen, and we support Africa's demands for this," it said.