At least 35 people were killed early Sunday when a passenger bus struck a fuel tanker in a head-on collision in the southern province of Zabul, officials said.
"The passenger bus was on its way from Kandahar to Kabul when it collided with a fuel tanker. In the accident, 35 people were killed and more than 20 others were wounded," Zabul's Governor Bismillah Afghanmal told AFP.
The collision sparked an inferno and many of the victims, including women and children, were burned beyond recognition, he said.
Some of the wounded were rushed to hospitals in provincial capital Qalat as well as neighbouring Kandahar province, said Ghulam Jilani Farahi, deputy Zabul police chief.
The Kabul-Kandahar highway passes through militancy-prone areas and many bus drivers are known to drive recklessly at top speeds so as not to get caught in insurgent activity.
Afghanistan has some of the world's most dangerous roads, often in dilapidated condition and traffic rules are seldom enforced.
Many in the country rely on old and rickety passenger vehicles, meaning that high casualty road traffic accidents are common.
In May at least 73 people were killed Sunday when two passenger buses and an oil tanker burst into flames in a head-on collision in eastern Ghazni province, in one of the worst road accidents in the war-battered nation.
And in April 2013 a bus hit a wrecked fuel tanker in the southern province of Kandahar, killing 45 people.
The World Bank last November signed off a $250 million grant to upgrade roads crossing Afghanistan's Hindu Kush mountains, crucial trade links that are often closed in winter by snow.