They said that they searched his house in response to suspected RAAD activity in the Creggan area, and insist that two males were seen running into Mr Campbell's house.
"I have been condemning what RAAD have been doing for the last number of years, I had forecast that there was going to be a death before people woke up to what was happening, " he said.
The newspaper said the Real IRA had been joined by Republican Action Against Drugs (RAAD) and a coalition of independent armed republican groups and individuals, some of whom are believed to have been involved in the murder of 25-year-old Catholic Constable Ronan Kerr in 2011.