Cape Town: President Robert Mugabe has offered a $US300,000 reward to anyone who can unmask an anonymous whistleblower behind a string of leaks about alleged Zimbabwean government assassination plots, corruption and plans to rig this month's election.

The well-informed mole, who calls himself "Baba Jukwa" and appears to be operating from within the heart of the regime, began posting revelations on a Facebook page four months ago.

Zimbabweans enjoy accessing the internet to read about Baba Jukwa in Harare. Baba Jukwa's name is whispered in buses, bars and on street corners by Zimbabweans eager for the inside scoop on President Robert Mugabe's ruling party. Credit:AP

The page has been viewed more than a million times and he has amassed more than 239,000 followers, with hundreds of responses and shares to every update. Efforts to track down the mole have so far failed. His postings have accused government ministers of corruption and senior police chiefs of brutality, publishing their private mobile telephone numbers.

Reassuring government statements about 89-year-old Mr Mugabe's health have been contradicted regularly, so infuriating the president that he offered the reward for exposing the mole - details of which were revealed by Baba Jukwa.