A signalling fault is delaying rail services between Norwich and London Liverpool Street.
The fault, which is at Swainsthorpe, between Diss and Norwich, is delaying services by up to 20 minutes.
Network Rail engineers are on their way to rectify the fault.
Services towards Norwich are delayed by up to 10 minutes and 20 minutes towards London Liverpool Street.
Abellio Greater Anglia say the disruption is likely to continue until 11.30am at the earliest, and apologised for the disruption.
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