A train derailment in Wellington delayed many of the capital's rush hour commuters this afternoon.

A Kiwirail spokeswoman said one wheel of a Ganz Mavag train had come off the rails inside the Wellington rail yard, which had prevented other trains from getting out of the yard to service rush hour.

''It's not actually blocking any of our commuter lines,'' she said.

Eight services were cancelled while many others experienced delays.

To compensate, KiwiRail extended some of its shorter services to stop at all stations.

It had also replaced some services between Wellington and Johnsonville with buses.

Services were departing on time by 6:45pm but outer stations were expected to experience delays up until 7:30pm.

SERVICE CHANGES

The following services have been replaced by buses:

- The 4:19pm service from Wellington to Melling

- The 4:32pm service from Wellington to Johnsonville

- The 4:45pm service from Melling to Wellington

- The 4:56pm service from Johnsonville to Wellington

- The 4:59pm service from Wellington to Melling

- The 5:23pm service from Melling to Wellington

- The 5:24pm service from Wellington to Johnsonville

- The 5:48pm service from Johnsonville to Wellington

Tranzmetro earlier advised the 3:40pm service from Wellington to Johnsonville was cancelled.