By Jeremy Cooke
BBC News, New York
Passengers using the New York subway are to be subject to random searches in a new security measure designed to reduce the threat of terrorist attacks.
Manhattan commuters will be affected
The city's mayor, Michael Bloomberg, announced the move hours after the latest bombings in London.
He admitted that passengers would be inconvenienced, but added that such security measures were growing increasingly necessary.
Around 4.5 million people use the New York subway system every working day.
With more than 450 subway stations on the network, it is unclear whether the searches of passengers with bags or backpacks can be any more than a token deterrent.
Civil liberties groups have warned that random searches may be unconstitutional.
But the New York police chief Ray Kelly has offered a guarantee that the searches will be truly random and that passengers will not be selected because of their apparent race or religion.
The recent attacks on the Underground system in London have served as a warning that the threat against mass transit systems is serious and potentially deadly.