APN is a leading regional publisher in Australia.
In New Zealand it publishes the New Zealand Herald, nzherald.co.nz and other regional newspapers. Its assets also include the GrabOne transactional business and its NZME. radio stable includes NewstalkZB and Radio Hauraki.
The sale effectively unwinds the last of INM's Southern Hemisphere investments instigated under Sir Anthony O'Reilly's control, with INM having sold its substantial South African media assets in 2013.
In 2013, INM struck a debt-for-equity deal with its bankers after reporting a loss in 2012 of 254.9 million ($368 million). Among the conditions was repayment of debt through asset sales.
In Wednesday's transaction, INM sold 191.5 million APN shares and O'Brien's private investment vehicle, Baycliffe Holdings, sold 125.8 million shares.
Australian funds management company Allan Gray this month said it had reduced its holding in APN from 17.7 per cent. The ASX-listed shares have climbed 52 per cent in the past 12 months.
Last month APN put off the public share float for its Kiwi business, NZME.