Detectives investigating the suspected payment of police for information arrested a serving officer and three other men on Saturday, and searched the offices of Rupert Murdoch's newspapers.
The investigation is linked to the police probe into phone-hacking at the News of the World, which Murdoch shut down in July after it emerged journalists had listened to the phone messages of thousands of people.
London's Metropolitan Police said Saturday's operation was sparked by information supplied by Murdoch's News Corporation media empire.
Three men, two aged 48 and one aged 56, were held in dawn raids in London and Essex, near the capital, on suspicion of corruption, aiding and abetting misconduct in a public office and conspiracy in relation to both offences.
"A fourth man, aged 29, was arrested at his place of work at a central London police station on suspicion of corruption under the Prevention of Corruption Act 1906, misconduct in a public office and conspiracy in relation to both these offences," the Met added in a statement.
It confirmed he was a serving officer in the Met's Territorial Policing command, and was currently being questioned at south London police station.
Officers had searched the homes of those held "and are also carrying out a number of searches at the offices of News International", the News Corporation subsidiary which operated the News of the World, the statement said.
A total of 12 people have been arrested in connection with Operation Elveden, the police investigation into the alleged payments, while a further 17 have been detained under Operation Weeting, the probe into phone-hacking.
Former News of the World editors Andy Coulson, a one-time aide to Prime Minister David Cameron, and Rebekah Brooks, later News International's chief executive, were among those held over phone hacking. They deny any wrongdoing.
The scandal erupted in July when it emerged that journalists had targeted not just celebrities and public figures but also murdered schoolgirl Milly Dowler.
Murdoch responded by closing the 168-year-old News of the World, and Cameron ordered a wide-ranging inquiry into the media ethics and practices.