The United States is reeling from a horrifying round of terrorist attacks in New York and Washington. Suicide aircraft attacks on the twin towers of the World Trade Center and the Pentagon have left untold numbers injured or dead and thrown the cities into chaos.

It began at the height of a morning rush hour in the nation's largest city. A plane, reportedly a hijacked American Airlines jet, slammed into one tower of the 110 story World Trade Center. As smoke and flames poured out of the building and rescue workers battled to save victims, a second plane hit the other tower. The upper portions of the two towers have now collapsed. Huge clouds of smoke hang over Manhattan. The nearby Wall Street financial markets have shut down.

A short time later, another plane struck the Pentagon, touching off a massive explosion and fire, and tearing a hole in one side of the historic building. The Pentagon, White House, and most other government buildings have been evacuated, sending thousands of scared federal workers into Washington streets. The capital is in virtual gridlock, with people jamming the roads and police sirens wailing.

President Bush labeled the incidents as "an apparent terrorist attack on our country" and "a national tragedy." He vowed "terrorism will not stand" and immediately broke off a visit to Florida to return to Washington. Police and military forces all around the country are on alert. Special anti-terrorist units have been mobilized in many cities. The United Nations and the Sears Tower in Chicago were also evacuated.

Officials say there was no advance warning of the attacks, and so far there is no claim of responsibility. The Trade Center was the target of another terrorist strike eight years ago, a car bomb that damaged the building and caused casualties but did not bring either of the towers down. The city's mayor, Rudolph Giuliani, says there will be a tremendous number of lives lost in this attack. There is no word on casualties at the Pentagon.