New York, Dec 2 (DPA) Construction of a $250-million shield intended to protect New York's tunnels and bridges against terrorist attacks was nearing completion, media reports said Wednesday.

The four-year-old project was aimed at thwarting bomb explosions that would damage the vast network of tunnels, subways and bridges in New York City and surrounding states and threaten the millions of people who use them each day.

Media reports said contractors had been lining subway tubes, including the 10 subway lines running under the East River, with a metal shield that could resist the impact of explosion and prevent collapse and massive flooding, in addition to saving lives.

The reports said the Port Authority of New York and New Jersey was spending another $600 million to strengthen tunnels linking Manhattan with New Jersey running under the Hudson River.

The seven bridges spanning the East River and Hudson River on both sides of Manhattan island have also been strengthened to resist bomb attacks, the reports said.

New York's World Trade Center was destroyed Sep 11, 2001 by terrorists who hijacked two commercial airlines and crashed them into the twin towers. More than 2,700 people were killed in the attacks. Since then, local government authorities have been trying to build up security protection for the city's more than eight million inhabitants.