WATCH: Grace Mugabe, Zanu-PF very very cruel to 'ancient' Mugabe

Zimbabwean opposition leader and former finance minister, Tendai Biti, says President Robert Mugabe's wife, Grace and the ruling Zanu-PF party are cruel for pushing the nonagenarian to continue clinging to power, News24.com reported.

Mugabe, 93, quietly flew out of Harare early on Wednesday purportedly for Singapore in what his spokesperson George Charamba said was for a scheduled medical review - raising fresh concerns over the veteran leader's health amid speculation in the private media he left in a "bad state".

But speaking exclusively to New24 on Thursday Biti, the president of the opposition Progressive Democratic Party, a splinter group from the main opposition MDC led by Morgan Tsvangirai, said Grace and the factions in the ruling party were holding the 93-year old leader to ransom by making him stand in the next polls tentatively set for July 2018.

"The man (Mugabe) is a fossil," said Biti, who sat in Mugabe's cabinet during the coalition government from 2009 to March 2013.

"The pictures we saw from his birthday party in Matopo were not pleasing to say the least," he said, adding that Mugabe was visibly suffering from old age.

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"Grace Mugabe and the factions in Zanu-PF are cruel. They are setting Zimbabwe for a catastrophic implosion as the succession issue remains unresolved in that party. Zanu-PF and its factions are leading us to a war, a war which will be the result of selfishness of persons in Zanu-PF."

Zanu-PF is thought to have two distinct factions, Lacoste linked to vice president Emmerson Mnangagwa and G40 said to be fronted by Grace, party national political commissar Saviour Kasukuwere and former party spin-doctor Jonathan Moyo.

Lacoste is reportedly pushing for Mnangagwa to succeed Mugabe while G40 is said to be flatly against his ascendency to the throne but would prefer the veteran politician die in office. However, politicians linked to these camps have denied they belong to factions.

'Ill-treatment of the elderly'

On her part, Grace has intimated Mugabe could afford to rule even from the grave, stating Zanu-PF could also afford to field his corpse in the next polls as it emerges her husband probably intends to be life president for both party and the country.

But be that as it may, Biti charged that Mugabe's wife and her eke in Zanu-PF sought to protect their interests at the expense of "an aligning old and aged man". He said they should be held accountable for the "ill-treatment of the elderly".

"I repeat there are very, very cruel. They should just let the old man go home and rest, they should let him go and play with his grand-son Simba (the son of Mugabe's daughter Bona)."

Biti said rushing Mugabe to Singapore or any other Asian country for treatment, would prove futile in the long run, saying there was no cure for old age.

"The man is old, aged. The man is ancient. There is no treatment for old age. No-one has found a cure for old age. We all come, we all go."