Security tightened at UK sites in New York after London attack

New York police ramped up security at British sites across the city on Wednesday after an assailant fatally stabbed a policeman outside Britain's parliament and was then shot and killed by police.

Heavily armed officers and explosives-detecting dogs were deployed to locations including the British Consulate and the British Mission to the United Nations in Manhattan, senior New York Police Department officials told a news conference.

"You'll see a larger presence of the dogs at these locations, as well as (officers) armed with the long guns," said James Waters, the police department's counterterrorism chief.

Police Commissioner James O'Neill said that while authorities were concerned about copycat attacks, there was no specific threat to New York City on Wednesday.

LIVE UPDATE ON WESTMINSTER ATTACK HERE

Outside the British Consulate, officers stood guard wearing helmets and tactical vests and carrying semi-automatic rifles. Several police cars were parked nearby, their lights flashing.

Police long-gun teams were also deployed to New York's City Hall and Grand Central Station, the department said.

Four people died and at least 20 were injured in London after a car plowed into pedestrians and an attacker stabbed a policeman close to parliament in what police called a "marauding terrorist attack."

New York police previously boosted security at prominent sites around the city after large-scale attacks in Paris, Brussels and San Bernardino, California, out of an abundance of caution.

The U.S. Department of Homeland Security said it would lend support to Britain's investigation of the attack but that the U.S. security posture was unchanged.

"We are in close contact with our British counterparts to monitor the tragic events and to support the ongoing investigation," the department said in a statement.