All lines are currently blocked at Manchester Piccadilly, which is one of the country's busiest rail stations.
Protesters have been seen holding banners which read: "Stop Turkey from helping Isis terrorists' banners.
A spokesman for Network Rail said: "The station will remain closed until all protesters have been removed.
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"All trains at the station will remain until the station opens. Trains on routes using the station will be terminated short of destination."
Trans Pennine Express and Virgins Trains services, which both operate routes through South Yorkshire, are among those affected by the ongoing disruption.