Former South African president Nelson Mandela's condition has improved, although he remains critically ill, the government has announced.

Mr Mandela is "still in a critical condition in hospital but shows sustained improvement," president Jacob Zuma's office said.

Mr Zuma gave the update after visiting Mr Mandela at the Pretoria hospital where he is receiving treatment. During the visit, he told the anti-apartheid leader of the love and support of all South Africans that was displayed at the leader's 95th birthday celebrations on July 18.

The president also asked the nation to continue to keep Mr Mandela in its thoughts and prayers.

Mr Mandela, who was jailed for 27 years during white minority rule, was hospitalised on June 8 for a recurring lung infection.

On his birthday, well-wishers celebrated with worldwide tributes dedicated to him on a day declared by the UN as the Nelson Mandela International Day. In South Africa, many people performed community service to honour him.