A man fatally shot a former colleague near the Empire State Building and then was killed by police in a gun battle that wounded nine bystanders outside one of New York’s most popular landmarks.

US counterterrorism officials are chasing a credible but unconfirmed al-Qaida threat to use a car bomb on bridges or tunnels in New York City or Washington.

US police arrested a man following a bomb scare that emptied a Pennsylvania Station and disrupted train and subway services for around an hour.