South Africa on Sunday lifted restrictions on the sale of alcohol on weekdays and the movement of people between provinces as President Cyril Ramaphosa said a third wave of the coronavirus may have peaked.

Africa's most industrialised country, which accounts for over a third of total Covid-19 infections and 40% of deaths related to the disease on the continent, had seen a severe third wave of infections over the past month spurred by the Delta variant but case numbers began to decline in recent days.

"The latest figures suggest that we have largely passed the peak of the third wave of infections," Ramaphosa said in a televised speech to the nation, but cautioned that some provinces were still seeing a rise in cases.

He moved the country down to an 'adjusted level 3' of coronavirus restrictions from immediate effect, under a five-level system with five being the highest.

Under level 3, people can travel between provinces for leisure. Ramaphosa also announced that a night-time curfew would start an hour later at 10pm. It would still finish at 4am.

The sale of alcohol from retail outlets will be permitted from Monday to Thursday and restaurants will also be allowed to serve liquor, he said.

However, restrictions imposed on indoor and outdoor gatherings would be maintained.

Infection rates, after hitting a peak of about 26 500 cases a day in early July, have declined to an average of around 12 000 per day in the last seven days, with the worst hit province Gauteng, home to South Africa's biggest city Johannesburg, reporting a steep fall in new cases.

The government would also open up Covid-19 vaccinations to people in the 18 to 34 age group from September 1, Ramaphosa said.

South Africa will get 31-million doses of the Pfizer Inc and Johnson & Johnson vaccines over the next three months that will ensure the country has sufficient vaccines for the rest of the year, he said.

Ramaphosa said his government will offer R350 monthly relief under a grant to those affected by Covid-19 restrictions and by a week of violence and arson, one of the worst since the end of white-minority rule in South Africa.