London  - Former South African President Nelson Mandela has added his voice to the growing international condemnation of Zimbabwe, speaking of a "tragic failure of leadership" in the southern African country.

"Nearer to home we had seen the outbreak of violence against fellow Africans in our own country and the tragic failure of leadership in our neighbouring Zimbabwe," Mandela said in a dinner in London late Wednesday.

His intervention was welcomed by British commentators Thursday, who said Mandela's remarks had made the international isolation of the regime of Robert Mugabe complete.

Mandela, who left politics nine years ago, had been criticized in some quarters for failing to speak out against Mugabe.

The dinner, given to celebrate Mandela's 90th birthday, which falls on July 18, was attended, among others, by Britain's Prime Minister Gordon Brown and former US president Bill Clinton. (dpa)