The government said 37 people were injured after a fuel tanker caught fire, and the death toll was expected to rise.
At least 12 people were killed in an accident in the Salang Tunnel, which connects Afghanistan’s capital Kabul to its north, the authorities have said.
Thirty-seven people were injured on Saturday after a fuel tanker caught fire, said Molvi Hamiddullah Misbah, a spokesperson for the Public Works Ministry.
While the fire had been extinguished, Misbah said on Sunday that the death toll was likely to rise. The cause of the accident remained unclear.
“When we went inside the tunnel in the morning, we saw bodies that were not recognisable, as they were severely burnt. Women, men and children were among them,” Ajab Gul, an eyewitness, told the Afghan Tolo news agency.
The landmark tunnel is located about 90km (56 miles) north of Kabul and is a key link between the country’s north and south.
Military helicopters along with medics and first aid teams were sent to the scene, the Defence Ministry posted on social media.
Abdullah Afghan Mal, a senior health official in Parwan province, said many of the dead included women and children whose bodies were badly burnt. “Among the dead it was very hard to identify who was a male and who was a female,” he told the AFP news agency.
The 2.6-km (1.6-mile) long Soviet-built tunnel is an engineering feat that links Kabul and Afghanistan’s north, connecting the Indian subcontinent to Central Asia through the treacherous Salang pass, one of the highest mountain highways in the world at about 3,650 metres (12,000 feet).
The pass is often shut for days because of accidents, heavy snowfall and avalanches during the winter months.
In 2010, avalanches killed more than 150 people in the Salang pass.