South African doctors who performed a minor surgery on Zimbabwean Vice President Emmerson Mnangagwa reportedly said that they "detected traces of palladium poison which had partly damaged part of his liver".

According to NewsDay, sources close to Mnangagwa said that the doctors discovered that the deputy president consumed non-radioactive which could require a systems flush out over the next two months.

"The VP ingested potent, non-radioactive poison which has low quality palladium substances which caused minor liver damage and he had to undergo surgery…," one of the sources was quoted as saying.

The vice president, 74, was flown to South Africa last week for emergency medical care.

Mnangagwa, who was seen as a favourite to succeed President Robert Mugabe, fell ill at a rally where the president was speaking on August 12, suffering what appeared to be severe food poisoning.

Mnangagwa's main rivals

Citing unnamed sources, The Standard newspaper said Mnangagwa underwent surgery on Wednesday "to treat the alleged poisoning".

State media did not report on his return.

With Mugabe, 93, in increasingly frail health, speculation over his successor has focused on Mnangagwa, a veteran regime loyalist.

Mnangagwa's main rivals within the ruling Zanu-PF come from the younger "G40" group which is thought to back Mugabe's wife Grace as a potential successor.

The president, who often travels abroad for medical treatment, has refused to name a successor and repeatedly denounced factionalism within the party.

Zimbabwe is to hold elections next year, with opposition parties in talks to try to unite in order to field a single candidate to oppose Mugabe.