According to the letters sent to editorial boards of the HTV and RTL television stations and the dailies 'Vecernji List' and '24 Sata', this organisation announces new terrorist attacks against state property and politicians.
The letters read that terrorist acts will be carried out "according to political events" and that "politicians must be aware that the security and safety of citizens and tourists are in their hands, namely it depends on the decisions which they are going to make".
"Croatia's national interests must strengthen, and in case that General Ante Gotovina be handed over to the (Hague war crimes) tribunal, Croatia will have to face the biggest terrorist attacks," the threatening letters read.
They also said that the first threatening letter, which was sent in early May and which was not signed, was a test for security services.
Our network is using home-made bombs and we want to say that we are in touch with ETA and that several of its people are in Croatia, the new letters read.
The spokesman for the Croatian Interior Ministry, Zlatko Mehun, told Hina that editorial boards of some media had received the threatening letters and that they were taken by the police to check and analyse their contents and possible traces which could point to the sender.
A police investigation is under way and we cannot confirm whether they have any connection with threats from letters which were previously sent to the addresses of those media, or something else is the matter, Mehun said.
The letters were sent by regular mail.