* Arrests raise questions about Sun newspaper's future

* Rupert Murdoch to fly to UK, "totally committed" to Sun

By Mohammed Abbas and Kate Holton

LONDON, Feb 11 (Reuters) - British police threw Rupert Murdoch's scandal-hit News Corporation into fresh turmoil on Saturday by arresting five senior staff at the top-selling daily The Sun in a probe into journalists paying police for tip-offs.

The move is part of a wider investigation into illegal news gathering practices that has rocked Britain's political, media and police establishments and last year prompted the closure of the Sun's sister Sunday title, the News of the World.

Saturday's arrests came after the company passed information to the police, a move that infuriated staff and sparked talk of a witch hunt amongst journalists by a proprietor who previously celebrated their work.

Murdoch is due in London next week and is set to meet staff, a source familiar with the situation said.

Four current and former Sun staff had already been arrested last month, and the latest detentions raise questions about the viability of Britain's best selling daily.

News International chief executive Tom Mockridge sent a memo to staff saying: "I have had a personal assurance today from Rupert Murdoch about his total commitment to continue to own and publish the Sun newspaper."

Sun editor Dominic Mohan said he was "as shocked as anyone by today's arrests" but determined to keep fulfilling the paper's "duty to serve our readers".

The source said the arrests included the Sun's deputy editor, picture editor, chief reporter and two other senior staff. Police said a serving police officer was among a total of eight people arrested on Saturday and later released on bail.

The source said a defence ministry employee and a member of the armed forces were the others. The ministry declined comment.

MONDAY EDITION PLANNED

The current staff who were arrested in January have been suspended by the paper, and the same fate is likely to await those arrested on Saturday.

As no production staff have been arrested, the company should be able to get a paper published on Monday. Staff who were not due to work over the weekend volunteered their services to make sure the paper was produced, said a second source close to the situation.

Both sets of arrests resulted from information from News Corp's Management and Standards Committee (MSC), a fact-finding group the firm set up in a bid to rescue its reputation.

The MSC is working alongside up to 100 personnel from top law firms as well as forensic advisers and computer experts searching through more than 300 million emails, expense claims, phone records and other documents. Some 15 or 20 police are embedded with the team.

According to people familiar with the work of the MSC, the project could take at least another 18 months. Piles of paperwork that cannot fit in the offices are stored in warehouses at another, secret location.

"The MSC provided the information to the 'Elveden' investigation which led to today's arrests ... News Corporation remains committed to ensuring that unacceptable news gathering practices by individuals in the past will not be repeated," News Corp said in a statement.

Murdoch shut the hugely popular News of the World last year after a public outcry over revelations that its reporters hacked the voicemail messages of celebrities and victims of crime.

He had hoped the newspaper's closure would draw a line under allegations of malpractice, but the arrests of Sun staff have renewed speculation over the future of his newspapers, with rival publications warning of a "crisis" and "staff in uproar".

DAMAGING

Steven Barnett, professor of communications at Westminster University, London, said Saturday's arrests were particularly damaging because they included senior current staff and were not related to historical actions by former employees.

"This is huge. It will raise some very serious questions about the viability of the Sun .... You then start to ask questions about the extent to which News Corp, and Murdoch in particular, may want to start getting out of newspapers altogether," he said.

Murdoch also owns Britain's Times, which this year admitted that one of its former reporters had hacked an e-mail account, as well as the Wall Street Journal and New York Post among a host of titles across the English-speaking world.

The octogenarian also has publishing, television and film interests in Asia, Britain, the United States and elsewhere.

U.S. authorities are stepping up investigations, including an FBI criminal inquiry, into possible violations by Murdoch media employees of a U.S. law banning corrupt payments to foreign officials such as police, law enforcement and corporate sources..

London police said 40 people had been arrested in connection with three police investigations into illegal news gathering practices, but that no one had yet been charged.

Allegations of widespread phone hacking at the News of the World prompted Britain's parliament, where many accuse Murdoch of wielding too much political influence through his media empire, to summon him and his executive son James to explain themselves last year.

James Murdoch took charge of News International, the British newspaper arm of News Corp, only once the hacking had stopped but has been criticised for failing to stem the problem.

The scandal has already prompted the resignations of two top police officials, who resigned over the handling of initial investigations into media malpractice; of Rebekah Brooks, the chief executive of Murdoch's London papers; and of Andy Coulson, a former Murdoch editor who became Prime Minister David Cameron's media adviser.

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