Police divers and Mangaung fire rescue personnel are searching for two missing street children thought to have fallen into a strongly flowing river channel running through Bloemfontein, police said on Monday.

Captain Chaka Marope said four children were playing next to the channel, near the Wilgehof Primary School, when they apparently fell in at about 8am on Monday.

"Two managed to drift downstream and rescued themselves when they were near the railway lines in Wilgehof," he said.

The other two children, from a Bloemfontein place of safety, were still missing.

Police divers and the city's fire rescue personnel were looking for them.

Marope said the two children who reached safety were between nine and twelve years of age. The missing children were the same age.

Heavy rains have fallen in the Bloemfontein area since Sunday with 70 millimetres measured in the city on Monday.