Nepal on Thursday called for urgent international support after a catastrophic disaster killed more than 1,200 people and left thousands missing, saying the scale of the destruction underscored the need for climate justice.

Agriculture, Forests and Environment Minister Gita Chaudhary told a ministerial meeting of the world's least developed countries (LDCs) in Dili that 1,206 people had died and more than 4,216 remained missing after the disaster struck northern Rasuwa district on August 26.

About 60,000 people from 15,000 households had been displaced, she said.

The disaster destroyed 11 hydropower projects with a combined capacity of 749 megawatts, more than 100 bridges, 118 telecommunications towers and about 187 kilometres of national highways, Chaudhary said.

Preliminary estimates put economic losses at between $4 billion and $5 billion, while non-economic losses could be two to three times greater and, in many cases, irreversible, she said.

"The LDCs do not seek sympathy, we are seeking justice, solidarity and implementation," Chaudhary said.

Nepal has formally requested support from the international Loss and Damage Fund, established under the UN climate process to help vulnerable developing countries address climate-related losses.

Chaudhary urged the fund to consider the Rasuwa disaster for rapid-response assistance, saying the appeal would test whether the mechanism could respond quickly and directly to countries facing climate catastrophes.

She also called on developed countries to meet their climate-finance commitments under the Paris Agreement and urged deeper cuts in greenhouse-gas emissions, particularly by major historical and current emitters.

Nepal contributes little to global greenhouse-gas emissions but is highly exposed to climate-related hazards, particularly in its mountainous regions.

Chaudhary said preliminary evidence indicated that a rock-and-ice avalanche, followed by the sudden blockage and release of the river, had contributed to the disaster. The precise causes were still under scientific investigation.

The disaster struck the Bhote Koshi river in Rasuwa, near Nepal's northern border with China, sending a destructive surge downstream through the Trishuli river system.

Nepal has focused on search and rescue, relief, rehabilitation and reconstruction, mobilising security agencies, government officials, local communities and volunteers, Chaudhary said.

The minister called for greater regional cooperation on transboundary rivers, including improved observation and data-sharing, multi-hazard early-warning systems and more climate-resilient infrastructure.

She also urged the UN climate process to give mountains greater priority, arguing that mountain communities face particular risks because of fragile ecosystems, remoteness, poverty and dependence on climate-sensitive resources.

Nepal's appeal comes as LDC ministers prepare to take their demands to the next UN climate summit, COP31, in Antalya, Turkey.

"We cannot lose another one year," Chaudhary said, warning that climate disasters in mountain regions could have consequences far beyond national borders.

"Climate action is therefore not merely a matter of negotiation -- it is a matter of humanity, justice and survival," she said.