President Jacob Zuma led celebrations Sunday to mark the 20th anniversary of post-apartheid democracy in South Africa, saying it was closer to achieving the dream of a united multi-racial nation.

"Our country has done well," Zuma said at a ceremony held two decades after the first all-race election that saw Nelson Mandela become the country's first black president.

"We all have a good story to tell."

"We have moved closer to our cherished dream of a united non-racial, non-sexist and democratic South Africa," he said at the "Freedom Day" ceremony held in the gardens of the Union Buildings, the seat of government in Pretoria.

South Africa is now the most developed country on the continent and boasts among other things, a strong constitution and an independent judiciary.

But its successes have been sullied by mismanagement and high-level corruption blamed largely on the ANC-led government, as well as a legacy of racial inequality, poverty, rampant crime and a lack of basic services.

The government failings have become a rallying point for the opposition ahead of general elections on 7 May, the fifth since the end of decades of sanctioned racial oppression.

But Zuma -- who himself has been tarnished by corruption allegations -- used his speech to warn rivals not to dismiss the "tremendous" gains in the country of 51 million people.

"I am sure you all agree with me that working together in the past 20 years and the past five years, we have made South Africa a much better place to live in," Zuma said.

"We must not deny or downplay these achievements, regardless of our political differences... at any given time, including the election period."

However, Nobel peace laureate Desmond Tutu, while conceding that two decades of freedom have seen a "heck of an achievement", said he was pleased Mandela was not alive today to witness the slow pace of transformation.

"I'm glad that Madiba is dead," Tutu was quoted as telling South Africa's Sunday Times. "I'm glad that most of these people are no longer alive to see this."

"I didn't think there would be a disillusionment soon," he said.

Zuma meanwhile urged South Africans to turn out in their millions on May 7 for the parliamentary, presidential and local elections.

"Our freedom was not free. It came about through blood, sweat and tears. That is why we must defend it at all cost," said Zuma.

"We are succeeding to heal the wounds of our brutal and divided past."

Freedom Day was marked by a full military parade including a 21-gun salute and fly-pasts as well as prayers, music and dance.

A colourful cultural parade entered the Union Buildings gardens to the tune of the South African 2010 World Cup's official anthem Waka Waka (This Time for Africa).

The Union Buildings complex is where generations of apartheid leaders penned many of the racial laws that Mandela and others fought against for most of their lives.

For many South Africans, Freedom Day brings back sweet memories of the euphoria of the election on 27 April, 1994, when black, Indian and mixed race voters stood in long lines alongside whites to cast their first ever ballots.

Tutu has said the day felt like "falling in love".

FW de Klerk, apartheid South Africa's last president who shared the Nobel peace prize with Mandela, described the day as "our proudest moment as South Africans".

But 20 years on, the euphoria has died down and the country is counting both the gains and failures of the democratic era.

Despite the anger over graft and glaring socio-economic disparities under its rule, the African National Congress is expected to retain power on 7 May election.

The ANC's continued popularity is testimony of the fact that for many South Africans life feels incomparably better than it did under the white minority's racist apartheid system.

Over 15 million people receive government social grants, while the majority of blacks are largely free to live and work wherever they want and a new black middle class is burgeoning.

But economic inequality persists and has seen poor South Africans take their anger to the streets, protesting over a lack of basic services like water, sanitation, electricity and housing.

The country's vital mining industry has also been wracked by strikes over pay and conditions.