HELSINKI (Reuters) - Finland has to stop "protecting" what Turkey considers a terrorist organisation and take Turkey's security concerns seriously if it wants Turkey to accept it in NATO, Turkish President Recep Tayyip Erdogan's spokesperson told a Finnish newspaper on Tuesday.

       "The problem is not that Finland would not understand Turkey. Finland refuses to take Turkey's security concerns seriously," Communications Director of the Turkish President, Fahrettin Altun told Finland's largest daily Helsingin Sanomat by email.

       Turkey has objected to Finland's and Sweden's joining the Western defence alliance on the grounds they harbour people linked to the Kurdistan Workers Party (PKK) militant group and others it deems terrorists, and because Finland and Sweden halted arms exports to Turkey in 2019.

       Altun's words echoed what Erdogan's chief foreign policy adviser Ibrahim Kalin told his U.S. counterpart on Monday, calling for the two Nordic countries to "take concrete steps regarding the terrorist organisations that threaten Turkey's national security".

       "Eventually Finland's government must decide which is more important, to join NATO or protect these kinds of organisations," Altun told the paper.

       (Reporting by Anne Kauranen; Editing by Lincoln Feast.)