Flash flooding that followed heavy rains has killed nine people taking part in religious rituals in Johannesburg, emergency services said on Sunday.

A group of 33 worshippers had joined church rituals on the banks of the Jukskei river when the flooding stuck, said Robert Mulaudzi, spokesman for the City of Johannesburg Emergency Management Services.

"Two people were swept away and confirmed dead on the scene," he said.

"We continued the search this morning and have recovered seven other bodies," he added on Sunday.

Rescue workers and firefighters are still searching for missing people.

Sudden surges of water are common in this part of Johannesburg, where storms take place almost every night during the southern summer.