A broken down Caledonian sleeper train is causing severe disruption to passengers heading north.
The London Euston to Aberdeen service is blocking the line between Arbroath and Montrose, with no services running from Dundee to Aberdeen .
ScotRail said: "We're currently arranging assistance to remove the Caledonian Sleeper train from blocking the tracks."
The rail operator expects the problems from the broken down train to last until around 11am and has arranged some replacement buses.
Services from both Glasgow and Edinburgh to Aberdeen are affected.
The Serco-run Caledonian Sleeper service tweeted: "The Euston to Aberdeen service has stopped just outside Arbroath due to loco failure and a replacement loco is on the way.
"Caledonian Sleeper sincerely apologise for any inconvenience these disruptions may cause you and we are doing all we can to resolve these issues as soon as possible."
The firm said other services to Inverness and Fort William are running around an hour late due to "driver issues".
Passengers also faced travel issues in the Central Belt, as a broken rail between Bellgrove and Carntyne stations in Glasgow has led to delays and cancellations.
ScotRail services between Milngavie, East Dunbartonshire and Edinburgh on the line via Airdie and Bathgate were suspended.
Those from Helensburgh to Edinburgh on the same line were not running between Partick and Garrowhill.
Ticket acceptance has been put in place on some local buses.
ScotRail expects the disruption to last until 12.45pm and said staff are "on site and working hard to rectify the fault."
