The digital screens that show Sydney commuters real-time information about trains were hit by a "major" IT outage on Monday night, preventing passengers from receiving up-to-date timetable information.

Transport apps that provide the same information were also hit, leading to unconfirmed speculation that the train network's IT issues also affected the train location system, or TLS, which Sydney Trains uses to identify where trains are on its network in order to prevent incidents.

Sydney Trains reported delays of 10 to 15 minutes on three lines on Monday night - the T2, T4, and T8 - although it was unclear whether this was related to the outage.

The indicator boards at Sydney train stations are not working properly due to an IT outage. Credit:Kate Geraghty

"Due to a network-wide IT disruption some indicator screens and transport apps are not updating in real-time," Sydney Trains said on Twitter at about 8.30pm.