Rescue teams sifted through piles of rubble in New York and Washington on Wednesday, looking for survivors, as the United States coped with the aftermath of terrorist attacks that left thousands of people missing, and many presumed dead.
From the debris of the World Trade Center in lower Manhattan to the damaged Pentagon, America got down to the business of assessing the damage from the attacks, while trying to locate people who remain trapped.
Fire fighters and ambulance crews have been working around the clock, after two hijacked commercial planes crashed into the twin towers of the trade center, and a third, into the Pentagon on Tuesday. A fourth hijacked plane crashed in Pennsylvania.
Two of the hijacked aircraft were American Airlines flights, and two, United Airlines flights. US Attorney General John Ashcroft said American Airlines Flight 11, which had departed from Boston, bound for Los Angeles "was hijacked by suspects armed with knives."
A spokesman for President Bush's National Security Council, Sean McCormack, said the White House and the presidential jet, Air Force One, had been targeted by the terrorists. For security reasons, Bush was first flown to the state of Louisiana, before being transported to Nebraska, and finally to Washington on Tuesday night.
FBI crews moved in to investigate, at the disaster scenes in New York and Washington.
The Federal Aviation Administration (FAA) on Wednesday gave its approval for a partial reopening of United States airspace, after closing it for the first time in history following Tuesday's attacks. The move was aimed at allowing flights diverted on Tuesday to continue to their original destinations.
However, the FAA said it would maintain its ban on regular services indefinitely.
Authorities, meanwhile said it could be weeks before the final count of victims is known. Officials said as many as 800 people may have died at the Pentagon alone.
Rescuers hope to find survivors at the World Trade Center, where 50,000 people worked. Thousands of other people visited the center daily.
One rescue worker in New York told journalists he had "lost count of all the dead people" he had seen. "It is absolutely worse than you could ever imagine," another rescue worker said.
The mayor of New York, Rudy Giuliani, said two police officers had been pulled alive from the rubble. Emergency workers say they have received pleas for help via mobile phones from people trapped inside the remains of the 110-story twin towers.
Some members of the police force trapped in the rubble fired gunshots to signal their presence to rescuers.
"Acts of mass murder"
The US president, George W Bush, has vowed to hunt down those who committed the deadly attacks, and bring them to justice.
In a televised address to the nation, Bush condemned the "acts of mass murder" and said the US military was "powerful and prepared".
No terrorist organisation has yet claimed responsibility for the attacks, but US administration officials said early evidence pointed towards the suspected terrorist, Osama bin Laden.
Nato pledges full support
In a show of support, Nato decided for the first time in its history to invoke Article 5 of its charter. Nato Secretary-General, George Robertson said the article declares an "armed attack" on any member to be an attack on all.
As a result, the United States will receive full military support from the Alliance if it is determined that the attacks were directed from abroad.
Across the United States, Americans have been queuing for hours to donate blood for victims of the attacks, while the American Medical Association has begun compiling a list of doctors willing to volunteer to treat disaster victims.
Church services and all night vigils have been held in a gesture of solidarity for victims of the worst attack on American soil since the Japanese bombing of Pearl Harbour in 1941.
swissinfo with agencies