WARSAW (Reuters) - Railways ground to a halt in many places across Poland on Thursday, hit by a widespread traffic control system outage, operator PKP PLK said, disrupting an important means of transport for refugees fleeing Ukraine.

       Infrastructure Minister Andrzej Adamczyk said that railway workers were dealing with the situation and normal service would be resumed as soon as possible.

       Almost 2 million people have fled to Poland from Ukraine since Russia launched its invasion on Feb. 24. Poland has offered free rail tickets to refugees, allowing them to travel to stay with friends and family around the country.

       "Regarding the transport of refugees, which has been the key task of the railway over the past few days, we are in full coordination of the process together with the ministry of infrastructure ... so that the process is not halted and can be carried out to the extent possible," PKP PLK deputy chief executive Miroslaw Skubiszynski told reporters.

       The traffic control outage was nearly nationwide, affecting 820 km (510 miles) of track, he added.

       (Reporting by Pawel Florkiewicz and Karol Badohal; Editing by Nick Macfie)