Scotland Yard said in a statement Wednesday it uncovered another suspected conspiracy to intercept voicemail messages that allegedly occurred in 2005 and 2006, The Guardian reported.
All six are journalists or former journalists, police said. Two reporters work for The Sun.
Police said the six were being questioned at police stations in London and Cheshire and their homes are being searched.
"Detectives on Operation Weeting have identified a further suspected conspiracy to intercept telephone voicemails by a number of employees who worked for the now defunct News of the World newspaper," the Scotland Yard statement said.
Police said the alleged phone-hacking victims were not previously notified, confirming that it was "part of the new lines of inquiry."
Mike Darcey, chief executive of Sun publisher News International, emailed staff to confirm the arrests, The Guardian said.
"As always, I share your concerns about these arrests and recognize the huge burden it places on our journalists in the daily challenge of producing Britain's most popular newspaper," he wrote. "I am extremely grateful to all of you who succeed in that mission despite these very challenging circumstances."