Talks at the COP30 climate summit in Brazil were disrupted on Thursday after a fire broke out in the venue, triggering an evacuation just as negotiators were hunkering down to try to land a deal to strengthen international climate efforts.

United Nations Secretary-General Antonio Guterres had appealed earlier in the day for a deal from the summit in the Amazon city of Belem, welcoming calls from some for clarity on the hotly disputed subject of weaning the world off fossil fuels.

There are less than 24 hours until the scheduled end of the summit to find a consensus among nearly 200 participating countries.

Host nation Brazil has framed a deal as a crucial step towards ramping up international climate action and demonstrating that there is broad support to accelerate turning decades of promises and pledges from COP summits into action.

Shortly after lunchtime, however, security footage showed flames breaking out at an exhibition pavilion and spreading rapidly up an internal fabric shell that lined the walls and ceiling of the building, before being extinguished.

Thirteen people were treated for smoke inhalation at the venue, organisers said.

The local fire service said it was probably caused by electrical equipment, likely a microwave, and was controlled within six minutes. Thousands of delegates were evacuated as security staff formed a human barrier across the hallway.

Negotiations were not expected to resume until Friday morning, a source told Reuters.

Consultations between the presidency and negotiating blocs could continue on Thursday night, subject to safety assessments at the venue.

The summit already missed a self-imposed Wednesday deadline to secure agreement among the countries present on issues including how to increase climate finance and shift away from fossil fuels.

Brazil circulated a draft proposal for part of the COP30 deal among some governments on Thursday, which did not include a roadmap on transitioning away from fossil fuels.

Emissions from burning fossil fuels trap heat in the earth's atmosphere and are by far the biggest contributor to warming.

The draft proposal, seen by Reuters, included other elements for a deal.

It said countries would call to triple the financing available to help nations adapt to climate change by 2030, from 2025 levels. However, it did not specify whether this money would be provided directly by wealthy governments, or other sources including development banks or the private sector.

Some negotiators said they had been working on the draft text shortly before the COP venue was evacuated due to the fire. Others said it had not been shared with them.

It is common at COP summits for the presidency to thrash out a text with small groups of countries, before bringing all governments together to greenlight the final deal.

The two-week negotiation has become hung up on two issues – the future of fossil fuels and the delivery of climate finance – that expose criss-crossing fault lines between negotiating blocs from rich Western countries, oil producers and smaller states most vulnerable to climate change.

Taking their cue from Brazil, dozens of countries including both developed and developing nations have mounted a push for a roadmap setting out how countries should transition away from fossil fuels.

Others, including some fossil fuel-producing nations, are resisting.

The COP28 climate summit in 2023 agreed, after protracted discussion, to a transition, but nations have not mapped out how – or when – it will happen.

"I am perfectly convinced that a compromise is possible," Guterres said. (Reuters)