The Daily Mail has linked the regional newspaper group with a move for Local Press, which as well as the Belfast News Letter also owns the Derry Journal, and the Leinster Leader Group, which owns newspapers including the Dundalk Democrat.
Local Press was formed when the Belfast and Derry titles were bought along with five others by private equity business 3i from Trinity Mirror for £46m in late 2003.
The deal would follow Johnston Press' £155m acquisition in August of Scottish Radio Holdings' Score Press business, bringing it 24 newspapers in Northern Ireland, five in the Republic and 16 in Scotland.
At the time of that deal, chief executive Tim Bowdler expressed interest in buying more newspapers in Northern Ireland and the Republic.
If the deal for Local Press goes through, Johnston would be the biggest newspaper publisher in Northern Ireland, rivalling Sir Anthony O'Reilly, who owns the Belfast Telegraph, another former Trinity Mirror title.
A spokesman for Johnston Press confirmed the interest but said the company would not comment on specific titles.
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