Hospitals in New York City and Washington DC were in chaos after the attacks on the World Trade Center and the Pentagon.

"People were vomiting from inhaling the debris that covered you like a snowstorm," said Tally Goldstein, a Financial Times reporter at the scene of the New York attack.

"Merchants were letting people take refuge in their stores. Emergency workers battled through the dust. Half the people I saw being taken care of were emergency workers in the thick of it," she said. Doctors and hospitals were on alert for "tens of thousands of patients", adding that they expect the majority of injuries to be severe burns.

Rudolph Giuliani, mayor of New York, said: "Hospitals need all of the help they can get". He urged medical and emergency workers to come into work to lend a hand. As of noon EDT, he said that 50 hospitals in the city were being used as emergency treatment centres.

A police officer at the scene estimated that 80 per cent of the 50,000 people who work at the Wolrd Trade Center were probably in the buildings.

Officials in New York and Washington DC have said that they face a critical shortage of blood. Many area hospitals, including Cabrini Medical Centre, had set up makeshift blood donation centres.

Mr Giuliani was urging people to donate blood but at some locations in the city queues of workers waiting to give blood were growing and the wait was expected to run into hours.

An emergency room attendant at Beth Israel Medical Center's Singer Division said that while no victims had been sent there yet, doctors and nurses were on "full disaster alert."

Hospitals in Washington, DC are in a emergency "maximum alert" mode, after the attack on the Pentagon.