An error in the IT system of the railway provider Banedanmark means that almost all the regional and intercity trains in Zealand and Lolland have broken down.
"There's a major breakdown of our IT systems, meaning that no signals, speakers or traffic information works," national rail service DSB reports.
DSB couldn't say when the trains will start running again.
"Right now the trains have stopped at their nearest station and customers have to wait there. And since there is no prognosis of when they will work again, DSB has not yet decided if buses will offer a replacement service," DSB reports.
However, buses have sent to fill in for services between Klampenborg and Helsingør, Ekstra Bladet reports.
Meanwhile, the S-trains and the Metro in the Copenhagen area are still working as normal.