Services have been halted on Arriva Trains Wales between Holyhead and Bangor because of flooding.
Virgin Trains services are also affected. Buses are replacing trains.
There are delays of up to 30 minutes on Arriva Trains Wales between Abercynon and Aberdare because of a points failure at Mountain Ash.
Services are at a halt on Arriva Trains Wales between Bridgend and Cardiff Central as emergency services deal with an incident. A replacement bus service is running
Great Western Railway services are also affected.
Network Rail is advising passengers of disruption to services between Abergavenny and Cwmbran after signalling cables were stolen on Sunday night.
It says engineers have been working day and night on the task of replacing the stolen cable in the Little Mill area.
Emergency signalling arrangements will be in place until work is completed, which is expected to be tomorrow morning.
Patrols are being conducted and specialist cable theft officers are carrying out enquiries in the area to find those responsible for the theft, which has resulted in ongoing delays, disruption and inconvenience to passengers and the rail industry, while we continue to work closely with scrap metal dealers to identify those that deal in stolen metal.
Cable theft is not a victimless crime – far from it. Train delays and cancellations directly affect people going about their daily lives, such as getting to and from work, visiting family and travelling to hospital appointments...
...Trespassing on the railway is extremely dangerous and cable thieves risk serious injury or death. We want everyone home safe every day and we continually look for ways to protect the network from thieves, working with British Transport Police to prosecute anyone caught carrying out metal thefts.
Train services between Newport and Hereford are being affected after signalling cables were stolen.
There are delays of up to 30 minutes and some cancellations after the theft between Cwmbran and Abergavenny.
Emergency arrangements have been introduced to allow some services to run.
Services are suspended on Arriva Trains Wales between Bridgend and Rhoose Cardiff International Airport because a vehicle has hit a bridge.
British Transport Police have released a CCTV image of a man they want to speak to in connection with the incident.Read the full story ›
There are delays of up to one hour on Arriva Trains Wales between Llanelli and Milford Haven, and between Llanelli and Pembroke Dock.
It is because of a broken down freight train between Carmarthen and Whitland.
Services have resumed on Arriva Trains Wales between Cardiff Central and Barry Island, and between Barry and Bridgend.
Over running engineering works between Cogan and Bridgend have been completed.
Services have been suspended on Arriva Trains Wales between Aberystwyth and Machynlleth after a person was hit by a train.
Disruption is expected to continue until 09:15.
Road transport is being arranged to run between Machynlleth and Aberystwyth.
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