London (CNN) -- Authorities arrested eight people Saturday -- including five journalists of Britain's bestselling Sun newspaper -- as part of an inquiry into alleged illegal payments to police and officials.
The other three are a police officer, an employee of the Ministry of Defence and a member of the armed forces, the Metropolitan Police said.
A search was carried out at News International's offices in east London, the police said, as well as the homes of those arrested. News International, which owns the Sun, is a U.K. subsidiary of media mogul Rupert Murdoch's News Corp.
Following the arrests, Murdoch, chairman and CEO of News Corp, issued a personal assurance to one of his executives to continue to own and publish The Sun newspaper, according to an internal staff memo sent by News International Chief Executive Tom Mockridge.
Mockridge also said he was "very saddened" by the arrests of deputy editor Geoff Webster, picture editor John Edwards, chief reporter John Kay, chief foreign correspondent Nick Parker, and John Sturgis, who is a news editor.
Late Saturday, three of those men -- ages 39, 47 and 52 -- were released after posting bail, said police, who didn't name any of the arrested journalists. The other two journalists remained in custody late Saturday, police said. All five were arrested at their homes, police said.
"I understand the pressure many of you are under and have the greatest admiration for everyone's continued professionalism," Mockridge wrote.
"The Sun has a proud history of delivering ground-breaking journalism. You should know that I have had a personal assurance today from Rupert Murdoch about his total commitment to continue to own and publish The Sun newspaper.
"Today we are facing our greatest challenge," Mockridge said.
The Sun's editor, Dominic Mohan, said in a statement: "I'm as shocked as anyone by today's arrests but am determined to lead The Sun through these difficult times.
"I have a brilliant staff and we have a duty to serve our readers and will continue to do that. Our focus is on putting out Monday's newspaper."
Mohan has said the paper has a readership of more than 7.7 million.
The arrests are part of Operation Elveden, an investigation running in parallel with a police inquiry into alleged phone hacking by the media, the police statement said.
News Corp.'s Management and Standards Committee said it had provided the information to the Elveden investigation which led to Saturday's operation. Elveden has been widened out to include alleged corruption involving public officials, as well as the police.
The five journalists, with ages between 45 and 68, were arrested at their residences in London, Kent and Essex on suspicion of corruption, aiding and abetting misconduct in a public office, and conspiracy in relation to both offenses, police said.
News Corp. said in a statement that it "remains committed to ensuring that unacceptable news gathering practices by individuals in the past will not be repeated."
The other three suspects were arrested on suspicion of corruption, misconduct in a public office, and conspiracy in relation to both these offenses.
A 39-year-old officer with Surrey Police is being questioned at a London police station, the Met Police said.
The Ministry of Defence employee, a 39-year-old woman, is being questioned at a police station in Wiltshire, as is the member of the armed forces, a 36-year-old man.
The police said the operation "relates to suspected payments to police officers and public officials and is not about seeking journalists to reveal confidential sources in relation to information that has been obtained legitimately."
The Ministry of Defence said it was a matter for the Metropolitan Police and that it could not comment on an ongoing police investigation.
The latest arrests come two weeks after four current and former Sun employees and a London police officer were arrested in connection with Operation Elveden.
News Corp. established its Management and Standards Committee in the wake of the summer 2011 scandal over alleged hacking of voicemail which led to the closure of the News of the World Sunday tabloid.
The revelation that a murdered 13-year-old girl's phone was hacked by journalists in search of stories -- and that many other crime and terror victims, politicians and celebrities had also been targeted -- prompted widespread outrage in Britain.
News Group Newspapers, part of News International, paid out hundreds of thousands of pounds this week to settle lawsuits over phone hacking from celebrities and politicians, including a former Tony Blair spokesman, Alastair Campbell.
The latest settlements meant News Group Newspapers has settled 59 of the 60 lawsuits against it.
British Prime Minister David Cameron set up an independent inquiry into press ethics and practices in response to the scandal.
Mohan defended his newspaper in testimony before the Leveson Inquiry earlier this month.
"The Sun is a private enterprise that performs a public duty with a public interest: to inform a mass readership so that British democracy can function properly," he said in a written witness statement.
"The Sun is occasionally boisterous and often cheeky but it is always a loyal companion to our readers, male and female. It relates to them in a more passionate way than any other title and in doing so it has become Britain's best-selling newspaper."
Two parliamentary committees are also investigating the scandal.
There have been 17 arrests in relation to Operation Weeting, the phone-hacking inquiry, and 21 in connection with Operation Elveden. Three people have been arrested in connection with both investigations. A third police inquiry is investigating alleged email hacking.
No one has been charged.