Maputo - ANC deputy president Jacob Zuma on Wednesday broached the controversial subject of the death of Mozambican president Samora Machel in a plane crash in South Africa, saying it was unusual for a country's president to die in another country.

Delivering the keynote address in Maputo at a memorial service to celebrate the life of South African struggle hero Moses Mabhida, Zuma said it was ironic that Machel had died in South Africa in the same year that Mabhida had died in Mozambique.

"It is unusual that a president of a country dies in another country.

"His death remains unexplained," he said.

Referring to Wednesday's service, he said: "This is symbolic and it speaks volumes of the historic relationship between the people of South Africa and Mozambique, and between Frelimo (the Mozambican ruling party) and the ANC."

Machel and 34 colleagues died in a plane crash near the Lubombo Mountains at Mbuzini, Mpumalanga, on October 19, 1986.

At the time of his death there were suspicions of foul play by the South African government.

In February this year the ANC government announced that it would re-open the investigation into the crash.

"We owe it to the people of Mozambique, who assisted our liberation forces to topple apartheid and install the democratic dispensation that we have," safety and security minister Charles Nqakula said at the time.

In his 2006 State of the Nation address, president Thabo Mbeki twice referred to the incident as "a plane crash that still requires a satisfactory explanation".

Speaking at the service, Zuma thanked the people and government of Mozambique for the support rendered to the ANC during the liberation struggle.

Mozambique provided bases for the ANC's military wing, Umkhonto WeSizwe, for military training and to launch attacks on South Africa targets.

"To us, Mozambique was like a second home. We are linked by some historic events with this country. Mabhida spent most of his life here and he also died here."

Also thanking Mozambique for backing the South African liberation struggle, KwaZulu-Natal finance and economic affairs MEC Zweli Mkhize said Mozambicans had suffered reprisals from the apartheid government for hosting the ANC.

He said some Mozambicans had been killed in attacks by the South African Defence Force.

"At the funeral of Mabhida, there was an undertaking made by the late president Machel and the late ANC president Oliver Tambo that Mabhida's remains would be repatriated back to his homeland once South Africa was free.

"Today we are fulfilling that undertaking," said Mkhize.

Mabhida's remains, which were exhumed in Maputo on Tuesday, will be transported back to South Africa on Wednesday, where they will finally be buried in Pietermaritzburg on December 2.