The massive New York City public transit system has stepped up security measures after two suicide bombings in Moscow's underground train system killed at least 39 people. The police department says there has been no specific threat against the city's subway system, but additional security has been put in place as a precaution.
The additional coverage includes more armed officers and sniffer dogs patrolling subway stations as well as more frequent bag checks and increased surveillance of high-traffic areas.
Mayor Michael Bloomberg says all New Yorkers, including the more than 250,000 with Russian heritage, express their deepest sympathy to the victims of the Moscow train bombings. He says any terrorist attack reminds the city it needs to remain vigilant.
"The answer to what we're doing is we change it every day and for security reasons, obviously, we're not going to tell anybody what we are doing," he said. "But you can rest assured that we have great interest in what goes on around the world."
The two bomb attacks in Moscow occurred during Monday's busy morning rush to work. Russian officials say early indications are that the attacks were the work of militant groups from the Northern Caucasus.
The attacks, carried out by two women, have spurred transit officials in New York City, Washington D.C., Boston, Chicago and other U.S. cities to temporarily tighten security to deter copycats.
One subway rider in New York, Willma Matthews, says the attacks in Russia serve as a reminder of the vulnerability of mass transit.
"If someone wants to do something, I guess you can't stop people," she said. "You don't know what's under someone's coat."
Last month, an Afghan immigrant living in the western U.S. state of Colorado, Najibullah Zazi, pleaded guilty to charges of leading a plot to bomb the New York subway system.