By Chris Michaud
NEW YORK (Reuters) - Police manned checkpoints and set up radiological monitoring equipment in Manhattan and the city's other boroughs over the weekend in response to unverified threats by al Qaeda on the Internet of dirty bomb attacks.
The moves stemmed from an "unverified radiological threat," a police department statement said, adding that the city's alert status remained at "orange" and stressing the increased security was precautionary.
The checkpoints went up Friday night and continued on Saturday at transit points into and out of Manhattan including the Holland tunnel, which connects lower Manhattan with New Jersey.
Police had initially said the increased security was in response to threats of a dirty bomb attack on Friday evening near 34th street, where the Empire State Building, Madison Square Garden, Penn Station and Macy's draw tourists and commuters.
But Deputy Commissioner Paul Browne clarified on Saturday the information the department received was not specific to that neighborhood.
Uniformed police officers lined the streets by the entrance to the Holland Tunnel, scanning passing vehicles and questioning some drivers, most of whom seemed to find their presence reassuring.
"I'm glad to see them here," said one man behind the wheel of a van. "It means they're aware of any dangers and are doing something about it."
"These actions are like those that the NYPD takes every day, precautions against potential but unconfirmed threats that may never materialize," Mayor Michael Bloomberg said in a statement, stressing the reality of life since the September 11 attacks,
Authorities were responding to Internet chatter reported on Israeli Web site www.debka.com, which reported a rush of chatter on al Qaeda sites in recent days, including one saying there would be an attack "by means of trucks loaded with radioactive material against America's biggest city and financial nerve center."
Another mentioned New York, Los Angeles and Miami as targets, the Jerusalem-based DEBKAfile Internet news site reported.
In response, police stepped up use of radiological sensors to monitor the streets, water and air throughout the city with the help of boats and helicopters.
New Yorkers, accustomed to life under "code orange" -- the second-highest such level, below red -- mostly shrugged off any possible danger.
"It really seems like a lot of fuss about nothing much," said Paul Machado, who was walking near the Holland Tunnel after having had brunch with friends in Tribeca. "They've (the police and media reports) said the threat was unsubstantiated so no, I'm not concerned at all."
Carrie Cuiccio sounded a somewhat skeptical note as she made her way toward the Brooklyn Battery Tunnel into Manhattan, which was restricted to one traffic lane and was closed to all trucks.
"I can't really see how the action they're taking would really prevent anything," she said.
A spokesman for the Department of Homeland Security in Washington had also said the threat to New York was "unsubstantiated," and there was "no credible information telling us there is an imminent threat to the homeland at this time."
Flaga al-Kaidy
W Internecie opublikowano wiadomość, z której wynika, że al-Kaida planuje atak brudną bombą na Nowy Jork.

Nowojorska policja oświadczyła, że wiadomość była "niezweryfikowaną pogróżką" przeciwko Nowemu Jorkowi. Policja oświadczyła też, że gotowość na zagrożenie pozostanie na poziomie "pomarańczowym". Zabezpieczono mosty, tunele i stacje metra.

''Debka.com'' lub ''DEBKAfile'', izraelska strona internetowa, mówi, że zdobyła informacje o zagrożeniu przez chat na stronie al-Kaid 8 sierpnia. DEBKA twierdzi też, że jednym z zagrożeń będą "ciężarówki wyładowane radioaktywnymi materiałami, które będą użyte przeciwko największemu miastu Ameryki i finansowemu układowi nerwowemu".

Na stronie mówi się też, że nie tylko Nowy Jork może paść celem ataku brudnych bomb, lecz także inne miasta, jak Miami i Los Angeles.

Nie podano żadnego terminu, w którym spodziewany byłby atak. 2 sierpnia kampania propagandowa al-Kaidy, As-Sahab, ostrzegła o nadchodzącej "wielkiej niespodziance". Także w tym wypadku nie podano żadnej daty.