JUBA - At least 85 people were killed in South Sudan when a crowd tried to gather fuel from an oil tanker that had veered off the road on its way to a region west of the capital Juba, the presidential spokesman said on Thursday.

The incident took place on Wednesday as the truck was travelling to South Sudan's Western Equatoria region.

"Eight-five people are confirmed dead by the local authorities," Ateny Wek Ateny, presidential spokesman said, adding about 50 people were seriously injured.

Such incidents have happened before in a region where fuel tankers often have to travel long distances along potholed roads and pass through poor communities.

There are almost no tarmac roads in South Sudan, one of Africa's poorest nations, which has been mired in conflict since December 2013. Rebels and the government signed a peace deal in August, although the ceasefire has already been violated.

Ateny said Wednesday's incident was not related to the conflict. "This was an accident," he said, adding the tanker had veered off the road and later exploded with a crowd around it.

In June 2013, at least 30 people were killed and scores more injured when a broken-down fuel tanker exploded on a highway in Uganda while they were trying to siphon fuel.