Four people have died while battling a wildfire in Bromo Tengger Semeru National Park in East Java, Indonesia, after being trapped by thick smoke and rapidly spreading flames.

The Indonesian Forestry Ministry confirmed the deaths on Friday, saying two other people sustained serious burns during the firefighting operation on Thursday.

Two of the deceased were national park officers, while the other two were security personnel assisting the firefighting team, according to park spokesman Endrip Wahyutama.

The victims were among a team of 12 people comprising park staff, community fire brigade members and local volunteers who were attempting to contain the blaze.

Three people died at the scene, while a fourth died while being transferred to hospital. Two survivors with serious burns were taken to Dr Soetomo General Hospital in Surabaya for specialised treatment, while six others escaped unharmed.

Strong winds caused the flames to spread quickly through dry vegetation, trapping some members of the team in the affected area.

Rescue operations were complicated by the remote, mountainous terrain, which prevented vehicles from reaching the site. Emergency crews had to carry some victims on stretchers for approximately two kilometres to an accessible location.

Police said an investigation had been launched into the incident, including whether negligence or criminal wrongdoing contributed to the deaths. Investigators were gathering evidence and interviewing survivors.

The wildfire comes amid a broader surge in forest and land fires across Indonesia, where prolonged dry conditions and land-clearing activities have contributed to the spread of blazes.

The Forestry Ministry reported 799 high-confidence fire hotspots nationwide by Thursday evening, up from 372 recorded a day earlier. Many were concentrated in fire-prone areas of Sumatra and Borneo.

Authorities expressed concern about deteriorating air quality caused by smoke and haze, with some locations experiencing unhealthy to hazardous conditions.

The haze has also spread to neighbouring countries, including Malaysia and Singapore, raising concerns about respiratory health and cross-border environmental impacts.

The ministry said firefighting operations were being strengthened in affected areas, although smoke and poor visibility had complicated aerial water-bombing and cloud-seeding efforts.

The incident has renewed attention on the risks faced by firefighters and volunteers working to contain wildfires, particularly in remote areas where rapidly changing wind conditions and difficult terrain can hinder evacuation efforts.