Terrorist plot to flood Manhattan 'foiled by FBI'

American intelligence officials say they have foiled a nascent terror plot to blow up underground train tunnels running beneath the Hudson River that carry thousands of commuters between New York and New Jersey every day.

The conspiracy was described as an attempt to flood the Wall Street financial district with water from the Hudson, and to create havoc on lower Manhattan similar to the chaos Hurricane Katrina wreaked last August upon New Orleans.

Had the plotters ever enacted the plan, they would have been most unlikely to succeed because the river is lower than Manhattan.

The plot, apparently involving at least eight people overseas, was in its infancy when FBI agents monitoring internet chat rooms uncovered the plans. "We have disrupted a terrorist network in the planning stages of an attack," said a statement released by the FBI and Department of Homeland Security.

The bureau decided to "take it down" when the suspects appeared ready to move forward and begin surveilling the targets.

"This is a plot that involved martyrdom and explosives and some of the tubes that connect Jersey and lower Manhattan," said FBI Assistant Director Mark J Mershon.

"We believe we intercepted this group early in their plotting and, in fact, the plan has largely been disrupted." He said the investigation has been running for almost a year, and it did not appear the suspects had ever visited the US.

The FBI statement added that a "key suspect" connected to the case, Amir Andalousli, had been arrested by the authorities in Lebanon . A Lebanese security official said the 31-year-old suspect's real name was Assem Hammoud; that he had confessed to the plot after being arrested on 27 April; and that he was connected to al-Qa'ida.

Another Lebanese security official, speaking on condition of anonymity, claimed that Hamoud said he was acting "on a religious order from Osama bin Laden and said, 'I am proud to carry out his orders.'" Two other overseas arrests have also been made.

Democratic Senator Charles Schumer said this was "one instance where intelligence was on top of its game and discovered the plot when it was just in the talking phase".

Initial reports of the investigation, in The New York Daily News, claimed that the main target was the Holland tunnel in lower Manhattan, one of New York's major road tunnels.

But an American counterterrorism official said that investigators had found no evidence that the Holland tunnel was part of the plot. Mr Mershon said the group specifically mentioned only the PATH tube tunnels beneath the Hudson.

The head of homeland security, Michael Chertoff, said it was "never a concern this would actually be executed. We were all over this."

Two weeks ago, authorities announced the arrests of seven men suspected of plotting to blow up the Sears Tower in Chicago. In May, a man was convicted of plotting to blow up a subway station.