Despite the journalists' accreditation, the guards did not let the reporters enter the hall without explaining the reasons for the ban, with one of them saying only "You may not be there."
The Brussels Forum is an annual meeting of American and European political and intellectual leaders discussing urgent global problems. Heads of state, EU officials, MPs, senators, academics and commentators of influential publications attend the forum.
This year's three-day session that started Friday focuses on the financial crisis, climate change, energy security and civil freedoms.
The forum is organized with the assistance of the U.S. German Marshall Fund. European Commission President Jose Manuel Barroso, Swedish Foreign Minister Carl Bildt and World Bank President Robert Zoellick are among the participants.