HARARE (Reuters) - Zimbabwean Vice-President John Nkomo died in South Africa on Thursday after years of battling cancer, a Zimbabwean political source said, removing a potential successor to ageing President Robert Mugabe, who has his own health problems.

Nkomo, 78, was nominated for the joint number two position alongside Joice Mujuru two years after a fractious meeting of the southern African nation's ruling ZANU-PF party.

(Reporting By Cris Chinaka; Editing by Ed Cropley)