"We must not lose sight of the fact that information society has the potential to become a nightmare instead of a blessing," Mesic said.
Information is becoming the foundation of the authority, position and influence, the foundation of a threat to our civilisation, but also the foundation of its defence, Mesic said.
"Information, namely its malignant form - misinformation, is becoming a powerful weapon in the fight against political opponents, economic competition, but not against those of same views," he said.
According to Mesic, every country has the right and obligation to defend itself and its citizens from global terrorism.
But not a single country has the right to bring into question fundamental rights and freedoms which are part of a democratic society in which we live, namely which we aspire to become, Croatia's head of state said.
A three-day summit on information society is the second phase of a summit held in Geneva two years ago. It pooled 50 heads of state and prime ministers and more than 11,000 officials, information technology experts and business managers from wealthy and poor countries so as to put in motion a UN initiative aimed at increasing access to modern telecommunications and the Internet in developing countries.
The summit was also addressed by UN Secretary General Kofi Annan.