The government has stepped up efforts to stamp out fraud and corruption within its social security system, Social Development Minister Bathabile Dlamini said on Monday.

Briefing journalists in Pretoria, she said the state provided social grants -- through the SA Social Security Agency (Sassa) -- to over 15 million beneficiaries, with a total budget of R105 billion.

"Sassa has intensified mechanisms to reduce fraud and corruption within the social security system," she said.

From the beginning of June, the agency started a full re-registration of all social grant beneficiaries "on a comprehensive biometric identification system".

Social development director general Vusi Madonsela said the number of beneficiaries who might be receiving grants fraudulently was not known.

"We can only estimate, based on international standards... that there is an estimated 10 percent leakage. Whether or not it is 10 percent in South Africa remains to be seen. Over the years, we've estimated we could be losing plus-minus R2bn."

However, this was still being investigated.

Madonsela said he was confident the actual number "was far less than the 10 percent international norm".

On the cost of the re-registration process, he said this was not an additional cost, but was included in the current tender, which would cost the government R10bn over the next five years.

Earlier this year, Sassa awarded the national contract for grant payments to Cash Paymaster Services.

Madonsela said the contract was saving the government R800m a year on the cost of administering social grants.

Responding to another question, he was not able to say how many foreigners might be illegally drawing social grants in South Africa.

"During the re-registration process we will identify which people are not South African or not resident in South Africa."

To date, Sassa had stopped grant payments to 111 people identified as non-South Africans and not eligible for a grant.