TEHRAN -- Iranian Ambassador to the United Nations Mohammad-Javad Zarif said on Monday that the September 11 attacks proved that all nations are vulnerable to terrorist acts.

Zarif told BBC Radio that the fact that all countries are vulnerable to the scourge of terrorism is undeniable and this was proven to the world by last year's devastating terrorist attacks against the United States.

The September 11 attacks showed that terrorist acts have no boundaries, he said.

U.S. citizens, who had not been involved in any direct conflict for many years, suddenly felt seriously threatened after September 11, he added.

Therefore, the U.S. reactions to the attacks were more emotional than logical, he noted.

The BBC interview of Zarif was part of a special program to mark the first anniversary of the September 11 attacks on the World Trade Center and the Pentagon in which BBC will be airing the views of international celebrities about the September 11 events every day.

On Monday BBC also conducted interviews with UN Secretary General Kofi Annan and U.S. Deputy Secretary of State Richard Armitage.

Annan said that when he was first informed about the first airplane hitting one of the twin towers of the World Trade Center, he thought it was an accident.

He stated that when security officials advised him not to leave the house he did not take their proposal seriously, but when he saw the second plane hit the second tower, he was certain that it was not an accident.

The U.S. holds Al-Qaeda and its leader Osama bin Laden responsible for the Sept. 11 attacks.