US police patrolling in New York (Photo: THX/VNA)

The Metropolitan Transportation Authority will expand bag screening and deploy extra police patrols in the subway system. New York state Governor Andrew Cuomo said in a statement he had also directed authorities to increase security at airports, bridges, tunnels and other sensitive locations across the state.

The New York Police Department said it has been in contact with London law enforcement officials and has added officers, heavily armed, and bomb-sniffing dogs to the city's transit system.