Bill de Blasio, right, mayor of New York, and Governor Andrew Cuomo, centre, are shown the remains of a rubbish bin at the site of the explosion in the Chelsea neighborhood of Manhattan

An improvised bomb exploded at a railway station in New Jersey while it was being made safe in a fresh terror alert following an attack in New York in which 29 people were injured at the weekend.

A suspicious backpack spotted at the Elizabeth station late on Sunday was found to contain “multiple improvised explosive devices”, the FBI’s Newark branch said.

Bomb squad personnel at the scene of a controlled explosion near a train station in New Jersey AP

One of them detonated while bomb experts were examining it. No-one was hurt.

The incident follows an attack in the Chelsea neighbourhood of New York on Saturday and the discovery four blocks away of another bomb, made from a pressure cooker, which was defused safely.

Separately, a pipe bomb was found in Seaside Park, New Jersey, in a rubbish bin on the route of