A massive increase in projected government debt poses a "major threat" to financial stability in South Africa, the central bank warned on Tuesday, while problem mortgages were also a risk.

South Africa's government debt is now set to hit 82% of gross domestic product this year as the Treasury grapples with the impact of the Covid-19 pandemic.

In its bi-annual review on the soundness of the financial system, the South African Reserve Bank (SARB) said this meant close links between the financial sector and government were now a serious worry.

"The interconnectedness between the financial sector and the sovereign has emerged as a major threat to financial stability in South Africa," the document said.

Domestic banks hold 23% of total government bond holdings and pension funds account for a further 29%, meaning any deterioration in the public finances has a perceived impact on these institutions' own credit worthiness, it said.