The US President Barack Obama has shaken hands with Cuban President Raul Castro at a memorial service for Nelson Mandela.

The handshake between the leaders of the two Cold War enemies came during a ceremony in Johannesburg that is largely focused on Mr. Mandela's legacy of reconciliation.

Mr. Castro smiled as the US leader shook his hand on the way to the podium to pay tribute to the late South African president, a global symbol of peace.

It was an unprecedented gesture between the leaders of two nations that have been at loggerheads for more than half a century.

It was Mr. Obama who offered the handshake in a new sign of his willingness to reach out to US enemies, a US official told the AFP news agency.

The US and Cuba have recently taken small steps toward rapprochement, raising hopes the two nations could be on the verge of a breakthrough in relations.

The ceremony in memory of Mr. Mandela, who died on Thursday at age 95, gathered heads of state from around the world.

Mr. Obama was also shook hands with Brazilian President Dilma Rousseff, who has clashed with the US over alleged National Security Agency spying.