An unprecedented and highly orchestrated series of attacks Tuesday turned the twin World Trade Towers in New York into piles of rubble, severely damaged the US Department of Defense's Pentagon building near Washington, DC, and prompted officials to close all US air traffic for the first time ever. The attacks also shuttered U.S. financial markets, brought major cities in the country to a standstill, snarled telecommunication networks, swamped the Internet and left much of the world reeling in horror, anger, fear and disgust. Digit is suspending all news activities today as a mark of respect, and will resume service tomorrow. "Today, our nation saw evil, the very worst of human nature, and we responded with the best of America," US President George W Bush said in a televised speech Tuesday evening, local time, in which he also said that government offices will be open for business Wednesday in Washington, DC. "We will make no distinction between the terrorists who committed these acts and those who harbor them," he said. Up to 50,000 people worked in the twin towers, which had stood at 110 stories each, and were hit by two hijacked airplanes. Two other hijacked airplanes also crashed, one at the Pentagon building and another in Pennsylvania. Windows around New York bore signs pleading, "Give blood, people are dying." Manhattan was basically sealed off from the rest of the world, with mass transportation, bridges and roadways closed. New Yorkers are being urged to stay home from work Wednesday, when financial markets also will be closed again. About 270 New York firefighters, including the fire chief and the deputy fire chief, and 78 police officers, are missing and feared dead, although a somber Mayor Rudolph Giuliani in a late-night press conference declined to confirm numbers regarding emergency officials. Apart from those on the crashed hijacked airplanes, there still were no numbers related to overall casualties as of late Tuesday night. "When we get the final number (of dead), it will be more than we can bear," Giuliani said. He pledged support for Islamic residents of the city, who already have come under attack. "No one should engage in group blame," Giuliani said, adding that authorities will arrest those behind such attacks. There are known to be victims trapped alive in the rubble of buildings near the World Trade Center, police officials said at the press conference, though they declined to offer any additional information. Some sense of normalcy is expected to resume Wednesday in other cities, including Boston and Chicago, where workers were sent home Tuesday after the attacks and government offices shut down all but the most essential services. Major national sites, including the Washington Monument, the Statue of Liberty and the St Louis Gateway Arch, closed. As the day ended, churches across the country held special prayer and healing services that drew hundreds. No one as of late evening East Coast time claimed responsibility for the attacks, involving the four hijacked airplanes, two of which took off from Boston's Logan International Airport. The carnage began shortly before 9 am local time when American Airlines Flight 11 smashed into the north tower of the World Trade Center. That flight had left Boston at 7:59 am, bound for Los Angeles with 81 passengers and 11 crew members, according to the airline. A few minutes after 9 a.m., United Airlines Flight 175 slammed into the south tower. That flight, also bound for Los Angeles from Boston, carried 56 passengers and nine crew members. Also hijacked were United Flight 93, a Boeing 757 on its way from Newark, New Jersey, to San Francisco, which crashed north of the Somerset County Airport in Pennsylvania, with 38 passengers, two pilots and five flight attendants, and American Flight 77, which left Dulles Airport en route to San Francisco carrying 58 passengers and six crew members. That plane crashed on a helicopter pad at the Pentagon shortly after takeoff, according to reports. There were reports, though unconfirmed, of deaths at the Pentagon, which burst into flames and one side of it collapsed. The five-sided building is located in Virginia, just across the Potomac River from the nation's capital, and is the headquarters of the US Department of Defense. Intelligence sources were reported as telling CNN that there seem to have been attempts to divert the San Francisco-bound United airplane to crash at Camp David, Maryland, the presidential retreat. Reports throughout the day had said that a plane had crashed there, though that was not correct. It is not clear how the plan to divert the flight to Camp David ended, CNN reported. Also contrary to earlier reports, none of the planes was shot down by U.S. aircraft, CNN reported. By late evening, however, there still was not official confirmation that the United flight that crashed in Pennsylvania was related to the other three airplane crashes, although news reports assumed it was a foregone conclusion that all four hijackings are linked. As the story unfolded, first one and then the other tower of the World Trade Center, well-known features of the Manhattan skyline, collapsed. Soot and debris had taken over the air around the towers after the attacks. Some who were stranded in the towers were seen leaping from the buildings before the structures tumbled. Later Tuesday, Building 7 at the World Trade Center complex also collapsed. It had caught on fire from burning debris earlier in the day. The World Trade Center was the scene of one of the first major terrorist attacks on US soil when it was bombed in 1993, killing six and injuring hundreds. But nothing had prepared the nation - indeed, the world - for the magnitude of Tuesday's attacks. Military and government officials compared it to the Japanese bombing of Pearl Harbor on Dec. 7, 1941, which pulled the U.S. irrevocably into World War II. Immediately, government officials began speculating that terrorists linked to Islamic militant Osama bin Laden were behind the attacks. News reports said that bin Laden warned three weeks ago that American interests would be subjected to an "unprecedented attack." Bin Laden is wanted in the US for 1998 US embassy bombings in Kenya and Tanzania that claimed 224 lives and injured more than 4,000. Afghanistan's ruling Taliban movement said that bin Laden is not responsible for the attacks, according to news reports. Bin Laden is believed to be in Afghanistan. Officials of the Taliban renounced the attacks, as did Palestinian President Yasser Arafat. "It's an unbelievable disaster," he said, according to published reports. "It is touching our hearts." He offered condolences to the US and condemned the attacks. Earlier in the day, Abu Dhabi television reported that a call had been received from the Democratic Front for the Liberation of Palestine (DFLP), claiming responsibility for the World Trade Center kamikaze attacks, but the DFLP later denied responsibility. But some Palestinians on the West Bank were shown in television news footage celebrating word of the attacks. However, the predominant reaction seems to be horror, with world leaders expressing sorrow and offering the U.S. help. "Freedom itself was attacked this morning and I assure you freedom will be defended," President Bush said, speaking from Barksdale Air Force Base in Louisiana soon after the attacks when he also announced that the U.S. military is on high alert. "Make no mistake. The United States will hunt down and pursue those responsible for these cowardly actions." Reports from the Washington Post, the New York Times, CNN and newswires were used in this story.