Luigi Mangione denies murdering UnitedHealthcare chief executive

Luigi Mangione has appeared in court (Seth Wenig/AP)

The man accused of fatally shooting the chief executive of UnitedHealthcare has pleaded not guilty to murder and terror charges in a state case that will run parallel to his federal prosecution.

Luigi Mangione, 26, was shackled and seated in a Manhattan court when he leaned over to a microphone to enter his plea over the killing of Brian Thompson.