A man has been struck by a train between Kilburn High Road and South Hampstead stations.
He has been taken to hospital with life threatening injuries.
Police were called at 1.45pm and the London ambulance service also attended.
The incident appears to be at the bridge on Abbey Road at the junctions of Belsize Road and Rowley Way.
There are severe delays on London overground services between Euston and Willeden Junction.
More to follow
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