British Prime Minister Mr Tony Blair was one of the first leaders to condemn the spate of terrorist attacks in the United States today.
Mr Blair said: "We the democracies of the world will have to come together to eradicate this evil."
His sentiments were echoed throughout the world.
The Palestinian President Mr Yasser Arafat was prompt with his criticism of the attacks early this afternoon.
"I send my condolences, the condolences of the Palestinian people to American President Bush and his government and to the American people for this terrible act," Mr Arafat said.
While Russian President Mr Vladimir Putin conveyed his deep condolences to the American people today, condemning the "terrorist acts" in New York and Washington.
The United Nations Secretary-General Kofi Annan has also condemned the acts of terrorism but called for cool and reasoned judgment.
The statement was issued by the UN European headquarters in Geneva because the world body was evacuated in New York following the attacks. Annan was at his nearby residence in New York, his New York spokesman said.
"We are all traumatised by this terrible tragedy. We do not know yet how many people have been killed or injured, but inevitably the number will be high, Annan said.
"There can be no doubt that these attacks are deliberate acts of terrorism, carefully planned and coordinated - and as such I condemn them utterly. Terrorism must be fought resolutely wherever it appears," he said.
Annan concluded: In such moments, cool and reasoned judgment is more essential than ever. We do not know yet who is behind these acts, or what objective they hope to achieve. What we do know is that no just cause can be advanced by terror."
French President Mr Jacques Chirac cut short a visit to Brittany following the attacks saying it was essential he return to Paris.
Later in the afternoon, Afghanistan's Taliban ambassador to Pakistan condemned the attacks.
His condemnation was followed by a claim from a spokesman for Afghanistan's ruling Taliban saying Saudi dissident Osama Bin Laden could not be responsible for the attacks.
"What happened in the United States was not a job of ordinary people. It could have been the work of governments. Osama Bin Laden cannot do this work, neither us," Mr Abdul Hai Mutmaen said.
This evening Pope John Paul II expressed his sympathies to President George W. Bush. In a Vatican statement the Pope said he was praying to God that he "give the numerous victims eternal rest, and courage and strength to their families".
China also said it condemned the attacks, saying it was "horrified," state media reported.