South Africa's anti-corruption watchdog said on Monday it was investigating irregularities in government tenders during the coronavirus crisis.

The inquiries by the Public Protector come after the Special Investigating Unit launched a separate probe into tenders for personal protective equipment (PPE) in the province of Gauteng, the country's economic heartland.

South Africa has recorded more than a half a million cases of Covid-19, the most on the African continent, with the number of infections continuing to rise rapidly.

In recent weeks, local media have brimmed with allegations that politically connected individuals have benefited from government contracts for goods and services mobilised to contain the spread of Covid-19. President Cyril Ramaphosa's spokesperson and a top Gauteng health official had taken leaves of absence after being caught up in the scandals.

The Public Protector said in a statement that it was investigating a quarantine camp tender in Mpumalanga province, an allegation that KwaZulu-Natal province had procured PPE at inflated prices, and a claim that a lodge being used as a quarantine site in Eastern Cape province was owned by a government official, among other investigations.

It is also looking into complaints that people were denied Covid-19 grants on unreasonable grounds.

Ramaphosa said in a weekly newsletter to the nation on Monday that families and friends of politicians and civil servants winning state contracts contributed to perceptions of nepotism and abuse.

He said his government would not allow public funds "to vanish down a black hole of corruption".

Public Protector Busisiwe Mkhwebane, who heads the anti-corruption watchdog, has become a controversial figure since a series of court judgments criticising the way she has handled important investigations.

Mkhwebane's supporters say she has held top officials including Ramaphosa to account. Her detractors say she has targeted Ramaphosa and close allies on behalf of a faction in the governing African National Congress (ANC) that is more closely aligned with former president Jacob Zuma.

Mkhwebane denies her investigations are selective or part of an ANC factional battle. Her predecessor was instrumental in exposing state corruption during Zuma's decade in power.