The National Union of Media Workers on Tuesday reported three paper companies to the Fair Trade Commission, accusing them of colluding on price hikes.

The three companies -- Jeonju Paper, Paper Korea and Daehan Paper -- raised the price of newsprint paper beginning in May and supplied less product to certain newspaper companies that did not cooperate with their price raise, the union claimed.

"If the paper price rises amid financial difficulty, newspaper companies will pass the burden to the employees. The increase in production costs due to collusion may dampen the newspaper market and eventually lead to a crisis of democracy and freedom of press," the union said during the press conference.

The media union said it will closely monitor the FTC's investigation and will call for responsible handling of the situation through meetings with Park Bo-gyoon, the minister of culture, sports and tourism.