Twenty-six people were electrocuted on Wednesday when an overhead high-voltage cable fell into a drainage ditch at a market in DR Congo's capital Kinshasa, local authorities said, giving a provisional toll.

"The cable snapped and the live end of it fell into a ditch that was filled with water after morning rain. At present, 26 people have died from electrocution," Charles Mbutamuntu, the spokesman for the Kinshasa provincial government, told AFP.

The Kinshasa tragedy occurred as news broke of a massacre in the troubled east of the DR Congo in which at least 40 displaced people were killed late Tuesday by machete-wielding militiamen, according to a monitoring group and local sources.

At the popular Matadi-Kibala food market in the west of Kinshasa, "most of the people killed were traders and customers, and some passers-by," Mbutamuntu said. "The bodies are being taken to the morgue and an investigation has been opened to establish responsibility."

The Congolese presidency said on Twitter that "all light will be shed on the causes of this tragedy and those responsible will have to answer for it," adding that President Felix Tshisekedi had decided last month on "the rapid relocation of this market in view of the danger posed by its current location".

The national power company, SNEL, said in a press release that "a lightning strike severed a live cable".

An official of the state-owned company told AFP that "the law prohibits building or setting up under high-voltage lines, but the land ministry had illegally issued permits covering these spaces regardless".

Videos circulating on social media showed corpses slumped over market stalls with their legs immersed knee-deep in muddy water.

Christelle Zindo, one of the traders, said: "Every time there's a drop of rain, the water doesn't drain away but overflows onto the market because the ditch is blocked, and all the traders have to work with their feet in the water."

She lashed "the total indifference of the authorities" to the problem.

Electricity infrastructure in Democratic Republic of Congo is often poorly maintained.

In Kinshasa, a sprawling metropolis of more than 10 million people, several districts are prone to flooding during tropical downpours as a result of poorly maintained colonial-era drainage systems.