Speaking to Croatian Radio on Monday, Mesic said the murder of the returnee to Karin was probably a terrorist act carrying a certain message.
He called on the police to solve as soon as possible this case as well as the planting of explosive devices in Vukovar and Trpinja in eastern Croatia over the weekend.
Mesic was speaking to Croatian Radio reporters in Bakar, where he attended the opening of an economic zone.
Asked by a listener if the terrorists' intention was to slow down Croatia's integration with the European Union and keep the country within the Western Balkan framework, Mesic said it was difficult to say until the cases were solved.
"However, it is a fact that terrorists want Croatia to be isolated because Croatia can be plundered only when it's isolated."
The president said that unsolved murders and criminal and terrorist acts did the most damage to Croatia ahead of the summer tourist season.
Listeners were also interested in Mesic's position on Party of Rights (HSP) leader Anto Djapic's statement that the HSP could not agree to coalitions with Serb parties after recent local elections.
"I think Djapic is doing no favours either to himself or a possible coalition partner," Mesic said, telling Djapic that those dividing Croatian citizens by any key had no place in Europe.
The president said he met Prime Minister Ivo Sanader in the morning for talks on new ambassadors, the amending of the existing or drafting of a new law on intelligence service, and relations with the Hague war crimes tribunal, the latter only in terms of intelligence community performance and cooperation with foreign secret agencies.
Asked about his expectations of chief prosecutor Carla del Ponte's report to the UN Security Council next month about Croatia's cooperation with the tribunal, Mesic said he thought Croatia would be more convincing than before. "There's no reason for us to be hostages to one man who has shown he has no patriotism at all," he said, alluding to runaway indictee Ante Gotovina.
The president said he would attend the Igman Initiative meeting in Belgrade in June because he felt it was important for the region. He recently cancelled a visit to Belgrade because of a Chetnik rally. Today he underlined the importance of honouring historical truths, including about the WWII Chetnik movement.
The Igman Initiative pools nongovernmental organisations from Croatia, Bosnia-Herzegovina, and Serbia-Montenegro. Its aim is to improve relations between the three neighbouring countries and build confidence among different peoples and ethnic communities.