NUJ general secretary and Offaly's Seamus Dooley says the union is highly concerned.
Two reporters at the Sunday World newspaper are among six people who've received death threats from loyalist paramilitaries.
The West Belfast UDA told one of the reporters they'd be shot dead within days.
The National Union of Journalists says those behind the threats are "intent on silencing journalism in Northern Ireland".
Its assistant general secretary Seamus Dooley says the union is highly concerned: