President Robert Mugabe waits to address mourners gathered for the funeral of former cabinet minister and ZANU-PF member Cephas Msipa in Harare, Zimbabwe, October 22, 2016. REUTERS/Philimon Bulawayo

HARARE (Reuters) - Zimbabwean President Robert Mugabe, Africa’s oldest leader, criticized some ruling party officials on Wednesday for “shameless and unbridled” ambition in their quest to succeed him.

Mugabe, 92, who has ruled the former British colony since independence in 1980, has refused to name a successor, saying the party will do so when the time comes.

His age and frequent rumors about his health have stoked a scramble in ZANU-PF over who should succeed Mugabe, who has said he will seek re-election in 2018.

Looking frail and laboring through a 40-minute speech, Mugabe condemned what he called “dirty politics” in the party during an address to the ZANU-PF Central Committee ahead of a two-day annual conference starting on Friday.

“There is nothing wrong in expressing an ambition, an aspiration, aspiring for position in leadership or for any other higher post in the party,” Mugabe said.

“But I have, however, frowned upon shameless and unbridled ambition, which seeks to ride roughshod over others. The tradition of our party is never one of bickering over party positions.”

One faction is widely believed to be maneuvering to impose Mugabe’s wife Grace as a successor, another backs Vice President Emmerson Mnangagwa, who has the support of war veterans.

Political analysts say Mugabe has manipulated politics to set himself up as a president for life and fear instability if he dies in office before the matter of his successor is resolved.