More than 70,000 extra troops will be deployed in South Africa to help enforce a lockdown intended to stop the spread of conronavirus, national broadcaster SABC says.

Opposition leader John Steenhusien has tweeted a letter that President Cyril Ramaphosa wrote to parliament saying that he had decided to deploy an extra 73,180 soldiers because of an increase in reported cases across the country.

Initially, the president had approved the deployment of just under 3,000 soldiers to assist in the implementation of a strict lockdown.

Jogging, dog walking and alcohol sales have all been banned. But security officers have found it hard in some places to enforce the measures.

Defence Minister Nosiviwe Mapisa-Nqakula confirmed the letter's details on local radio, the AFP news agency reports.

"If you look at the numbers and the rate at which the infection has gone up, you will realise that at some point we may actually need the kind of human deployment which has never been seen before," AFP quotes her as saying.

There are 3,465 confirmed coronavirus case in South Africa and there have been 58 deaths.

Wow... pic.twitter.com/IiXg2Q5Hri

— John Steenhuisen MP (@jsteenhuisen) April 21, 2020