A Lebanese television network is on trial at a special U.N. tribunal, accused of obstructing justice by releasing identities of confidential witnesses in the long-running probe into the killing of former Prime Minister Rafik Hariri.

Al-Jadeed television and its deputy news director, Karma Khayat, pleaded not guilty to charges of contempt of court. The network says the case raises concerns about media freedom.

The proceedings began Thursday near The Hague in the Netherlands.

The network is accused of publishing a list of prosecution witnesses in the Hariri case in 2012, which the tribunal said could compromise the proceedings.

The 2005 suicide bombing that killed Hariri and 22 others was one of the Middle East's most dramatic political assassinations. Four Hezbollah members were charged in 2011 but have not been arrested.