The power failure at the stadium in the town of Kikwit occurred at around 2 am today, said witness Papa Mukalay who attended the concert.
"Everyone wanted to be the first to get out. It was total confusion," he said.
The provisional death toll by midday Friday was 23 and injuries were also reported, said government spokesman Lambert Mende. He said investigations into the cause of the power outage had been launched.
The festival was scheduled to last through Sunday, but the Bandundu provincial government said today the rest of the program would be cancelled.
"This morning activities have restarted quietly but people are in a state of shock," Mukalay said.