World leaders are reacting strongly to Tuesday's attacks on the World Trade Center in New York City.

Pope John Paul II called the attacks an "unspeakable horror" which has thrust the U.S. into a "dark and tragic moment."

"I hurry to express to you and your fellow citizens my profound sorrow and my closeness in prayer for the nation at this dark and tragic moment," says the pontiff.

British Prime Minister Tony Blair also expressed horror and has sent condolences to U.S. President George W. Bush.

"There have been the most terrible, shocking events taking place in the United States of America within the last couple of hours," Blair says.

"We can only imagine the terror and carnage there and the many, many innocent people who have lost their lives."

Israeli Prime Minister Ariel Sharon says his government has declared a day of mourning.

"Our hearts are with you and we are ready to provide any assistance at any time," Sharon told Americans.

French President Jacques Chirac expressed outrage, and assured the United States of France's support and sympathy.

"France is deeply upset to learn of the monstrous attacks that have just struck the United States," says Chirac.

"In these terrible circumstances, all French people stand by the American people. We express our friendship and solidarity in this tragedy."

United Nations Secretary General Kofi Annan calls the crashes "deliberate acts of terrorism, carefully planned and coordinated."

"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."

Chinese President Jiang Zemin has sent a message to Bush, and has expressed condolences to the family members of the victims of the attacks. He also expressed "grave concern" for the safety of Chinese in the United States.

Russian President Vladimir Putin expressed deep sympathy to the American people, calling the incidents a "terrorist act, this terrible tragedy."

Palestinian President Yasser Arafat also sent his condolences to Bush.

"We completely condemn this serious operation ... we were completely shocked. It's unbelievable, unbelievable, unbelievable," says Arafat.

Israeli Defense Minister Binyamin Ben-Eliezer told Israel's Army Radio it was "simply a tragedy."

"I sympathize with the American people," he said. "It's simply a terrible thing."

German Chancellor Gerhard Schroeder said: "the German people stands by the United States of America at this difficult hour."

"I want to express to you my deep condolences and my unlimited solidarity to you and the American people. Our sympathy goes to the victims and their relatives."

Europe's largest stock exchange has been evacuated. The Exchange Tower of the London Stock Exchange has been cleared as a precautionary measure, but trading will continue until the close of business.

United Kingdom stocks have suffered their biggest one-day drop since October 1987, when Black Monday occurred. The FTSE 100 in London lost 67-billion pounds or $98-billion US on Tuesday.

Also in London, buildings in Canary Wharf, the new financial district in the east part of the city, have been evacuated.

NASA has shut down Kennedy Space Center in Florida, although the agency says it has had "no indications of an imminent threat."

Major office buildings in downtown Los Angeles, including the Citibank Tower, the Arco Tower and the Bank of America building, were ordered evacuated Tuesday.

Disneyland in Anaheim has been closed, as well as Disneyworld in Orlando.

Many foreign embassies in Washington D.C. have closed, and have been told to send all personnel home.

The U.S. Secret Service told the Mexican embassy, three blocks from the White House, to send everyone home.

The Canadian embassy, on Pennsylvania Avenue, is open for business, but under a state of heightened security.