At least 35 people were killed in Afghanistan when a fuel tanker collided with a passenger bus, causing a massive explosion, according to local officials.

Sunday's incident happened on a major highway connecting the southern province of Kandahar with the capital city of Kabul.

Bismillah Afghanmal, provincial governor of Zabul province where the accident happened, told the AFP news agency that the passenger bus was on its way from Kandahar to Kabul when it collided with a fuel tanker in the Jildak area of Zabul.

"In the accident, 35 people were killed and more than 20 others were wounded," he said.

Ghulam Jilani Farahi, deputy police chief of Zabul, said authorities could identify only six bodies and the rest were completely burned, adding that the bus was carrying more than 60 people.

The driver of the oil tanker and a passenger died immediately after the truck burst into flames during the early morning hours on Sunday, officials said.

The Kabul-Kandahar highway passes through areas prone to conflict and many drivers are known to drive at high speed in the hope of avoiding attacks.

Risky roads

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 accidents are common.

In May, at least 73 people were killed when two passenger buses and an oil tanker burst into flames in a head-on collision in eastern Ghazni province, in one of the country's worst road accidents.

The World Bank last November signed off a $250m grant to upgrade roads crossing Afghanistan's Hindu Kush mountains, crucial trade links that are often closed in winter by snow.

Insecurity is growing across Afghanistan as the Taliban presses on with a 15-year battle against the Western-backed government.

Afghan troops have struggled to stave off nationwide attacks since NATO forces ended their combat mission at the end of 2014.

Source: Agencies