Kim Williams has overseen a programme of change at News Corp Australia
The chief executive of Rupert Murdoch's News Corp Australia has resigned after 20 months in the job.
Kim Williams, who took the role in December 2011, is to be replaced by Julian Clarke.
In an email to staff, Mr Williams said he made the decision with a "heavy heart and a mixed bag of feelings", but gave no specific reason for his decision.
He steps down with an election campaign underway in Australia.
Rupert Murdoch praised Mr Williams as "a steady and courageous leader at a time when our businesses have faced unprecedented pressure and economic challenges".
Few really know why Kim Williams has parted company with Rupert Murdoch. But there's speculation in the Australian media the resignation could be linked to some of News Corp's election coverage this week.
Kevin Rudd has accused Mr Murdoch and his senior executives of issuing his newspaper editors with a "directive" to get rid of the Labor government.
On day one of the election campaign News Corp's Sydney Daily Telegraph ran a front page photo of Mr Rudd with the headline "Kick this mob out." On Thursday the same paper depicted the prime minister as Colonel Klink, the bumbling World War II German officer from the 1960s TV series Hogan's Heroes.
Kim Williams may not have been comfortable with this. But commentators also say the non-newspaper man may have fallen victim to internal politics, losing a battle with Mr Murdoch's editors.
Mr Williams, who came from a pay-television background, oversaw a programme of cost-cutting and change that some observers said had put him on a collision course with newsroom editors.
Australian media reports also said the move came weeks after Mr Murdoch flew in a top lieutenant, Col Allan, to shake up his publications.
Mr Clarke, the new chief executive, is a veteran company man who headed up Mr Murdoch's Herald and Weekly Times group, which includes the Herald Sun tabloid.
Rupert Murdoch's News Corp is the dominant player in Australia's newspaper market.
With the election campaign underway, his Daily Telegraph tabloid has taken a strong stance against Prime Minister Kevin Rudd.
Mr Rudd, who replaced Julia Gillard as Labor Party leader in June, faces an uphill battle against the Tony Abbott-led Liberal-National coalition in the 7 September polls.
He has accused Mr Murdoch of interfering in the election to protect his commercial interests, citing his opposition to the National Broadband Network policy - claims a News Corp spokesman has rejected.
Source: BBC News - Business http://www.bbc.co.uk/news/world-asia-23628060#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa
