More than 100 people were killed in South Sudan when an oil truck exploded as a crowd tried to gather fuel from the vehicle after it had veered off the road, a regional official said on Thursday, a day after the incident.

In addition to those killed in Wednesday's blast, Charles Kisagna, the minister of information in Western Equatoria, said about 50 people were seriously injured.

"We don’t have medical equipment and these people may not survive because we do not have the facilities to treat the highly burnt people,” he told Reuters, adding the truck had been traveling from the capital Juba to the Western Equatoria area.

Such incidents have happened before in the east African 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.

Presidential spokesman Ateny Wek Ateny said Wednesday's incident was not related to the conflict. "This was an accident," he said.

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.