The truck was transporting fuel from neighboring Tanzania when it overturned at high speed late Friday in the village of Sange, around 20 miles (30 kilometers) north of the town of Uvira near the Burundi border. Sange is located between Uvira and the Congolese provincial capital, Bukavu, further to the north.
After the accident, "people came out and tried to siphon the contents of the tanker," said Madnodje Mounoubai, a spokesman for the U.N. peacekeeping mission, which has rushed troops to help evacuate survivors.
"A fire started, and the people trying to siphon the fuel were killed or injured," Mounoubai told The Associated Press. "Right now, we are talking about 220 dead and 111 wounded, but this is not the final toll. This is a very fluid situation."
A U.N. helicopter has so far evacuated 35 wounded to Bukavu, Mounoubai said. Other peackeepers were taking more wounded to nearby hospitals by ambulance.
Desire Yuma, a local Red Cross official in Bukavu, said Red Cross workers were still collecting charred bodies from the scene. The Red Cross says at 221 died and 214 were injured in the accident.
It was not immediately clear what caused the explosion.
Desperately poor people across Africa often descend quickly around damaged or disabled oil trucks leaking fuel on roads and highways, carting it away with plastic jugs, unaware of the danger of doing so.
The worst tragedies have occurred in the West African nation of Nigeria, where thousands have died as crowds siphoned fuel illegally from ruptured or pierced oil pipelines that subsequently exploded.