"Mr. Mazoka has died. All senior party executives are meeting now before a media announcement," an official at his United Party for National Development told Reuters.

Mazoka died of kidney complications early on Wednesday, a week after Lusaka newspapers said he had been admitted to a Johannesburg hospital for a routine medical check-up.

Mazoka lost narrowly to President Levy Mwanawasa in 2001 presidential elections when Frederick Chiluba stepped down after his final five-year term as president. He was expected to lead an opposition alliance challenging Mwanawasa in elections later this year when the incumbent will defend his post.