Emergency services are responding to what is believed to be a serious incident involving a train and a pedestrian in central Christchurch.

Police, firefighters and several ambulances were called to the railway crossing on Gasson Street, near Moorhouse Avenue, on Friday afternoon.

Witnesses reported seeing a stationary train on the tracks, with its lights still operating, while emergency crews worked at the scene.

One witness said three ambulances, a fire engine and multiple police vehicles had arrived, with further emergency vehicles heading towards the area.

Another witness said people gathered nearby appeared visibly shaken.

Traffic is reportedly heavily congested around Gasson Street and Moorhouse Avenue, with motorists advised to avoid the area.

The circumstances of the incident and the condition of the person involved have not yet been officially confirmed.

Police and St John have been approached for further information.

More soon.