The Ministry of Natural Environment and Climate Change reported on October 28 that the fire burned 504,960.4 hectares, about 5,050 square kilometers and more than twice the area of Tokyo. Of that, 448,993.6 hectares lay inside the Numrug Strictly Protected Area, meaning 76.4 percent of the reserve was affected. The reserve, in Khakhgol soum in Dornod province, sits in the transition zone between the western foothills of the Greater Khingan Range and Mongolia's eastern grasslands, near the China-Mongolia border, and is home to species including the Ussuri moose, black-billed capercaillie and Far Eastern taimen, along with more than 250 bird species.
The fire broke out on October 8 and was not fully extinguished until October 16. According to Mongolian authorities' preliminary investigation, a Mobicom vehicle's chassis became wrapped in dry plants, and prolonged driving caused friction and heat to ignite the grasses. Mobicom said its convoy entered the protected area to conduct 4G network communication tests near the Sumber-Rashaan border port. It initially sought to avoid responsibility, saying it had followed "complete legal procedures," before publicly apologising after public pressure escalated. It has now agreed to provide compensation once a joint working group assesses the loss and damage, while continuing to insist it held the proper permits and took necessary precautions.
The fire line approached the Chinese border and triggered a cross-border response under the 1999 China-Mongolia agreement on forest and grassland fire prevention. More than 3,400 professional firefighting and emergency personnel were mobilised in China's Inner Mongolia region, keeping the fire from crossing the frontier while leaving a passage open for wild animals. China is now demanding compensation for that effort from Japan rather than Mongolia. Liu Zhiyan, a researcher at the Institute of Ecological Civilization of the Chinese Academy of Social Sciences, said the grasslands of eastern Mongolia are highly interconnected with northern China's ecology, warning that a cross-border spread would bring huge economic losses and could trigger serious diplomatic disputes. Some analysts in Chinese media have raised concerns about information security around Japanese communication projects in sensitive border areas, but these claims have not been officially confirmed.
Japan's Chief Cabinet Secretary Kihara Minoru did not make an official statement until October 26, two weeks after the fire broke out. Three days later, Prime Minister Takaichi Sanae spoke by telephone with Mongolia's Prime Minister Uchral Nyam-Osor for ten minutes, the highest-level exchange between the two governments since the disaster. Takaichi said Japan "takes seriously the scale of the damage caused" and "extended her heartfelt sympathies to the people of Mongolia," adding that Japan "intends to provide a package of cooperation that contributes to the recovery of the affected areas, including the provision of necessary equipment to Mongolia and human resource development in the fields of recovery from the wild fires and environmental restoration." The package will be based on an on-site assessment by JICA forestry and natural environment experts dispatched on October 27. Official readouts from both governments said the call focused exclusively on bilateral relief and diplomatic matters, with no reference to China's firefighting deployment or the cross-border spillover risks.
Inside Mongolia, Uchral has called the fire a "serious ecological incident" and said "foreign investors have no privilege above Mongolian law," demanding a thorough investigation of how access permits to protected areas were granted and vowing to hold companies and officials accountable. Opposition MP Altangerel Oyunsaikhan has demanded that the judiciary freeze all of Mobicom's assets and financial accounts in Mongolia as collateral for ecological compensation. Former sumo wrestler Asashoryu (Dagvadorj Dolgursuren) says "blindly condemning the Japanese side is one-sided," and has urged the media to investigate the officials who issued permits for the convoy, suggesting local regulatory corruption. Dornod MP Otgonbayar Ukhnaa, whose brother is President Khurelsukh Ukhnaa, has firmly denied involvement and called the questions a politically motivated smear campaign.
In Japan, public opinion has criticised the government's slow response and accused it of double standards, while opposition parties and media have criticised Kihara's delayed statement; some have called the two-week silence a "national shame." Shimba Kazuya, secretary general of the Democratic Party for the People, said the incident goes far beyond corporate civil liability and demanded government intervention. Within the ruling Liberal Democratic Party, former State Minister for Foreign Affairs Nakayama Yasuhide argued that KDDI and Mobicom must assume full civil, financial and moral liability, but that this isolated operational failure should not compromise Japan's strategic relationship with Mongolia. Fellow LDP lawmaker Nagashima Akihisa noted the convoy entered under explicit administrative approval and was escorted by Mongolian border port authorities, and rejected Chinese state media demands for a formal apology to Beijing as an unverified political distortion.
The ecological damage is expected to be long-lasting. The soil's surface organic matter has been carbonised, its ability to retain water and nutrients greatly diminished, and the native vegetation seed bank suffered a devastating blow. When strong winds arrive in spring and autumn, the risk of desertification and sandstorms in the region will significantly increase. On cold, arid grasslands, full recovery of the native community is expected to take 20 to 100 years, with permanent species replacement possible in some areas. The disaster has also highlighted structural weaknesses in Mongolia's environmental governance, which is known for "heavy approval, light supervision" and "heavy firefighting, light prevention," with core protected areas left open to commercial vehicles during the autumn high-risk period. Environment Minister Sandag-Ochir Tsend admitted that complex terrain and logistics make on-site assessment after disasters difficult. Mongolia's remote areas have long relied heavily on satellite monitoring, with limited ground verification and emergency response capacity.