Germany issued tighter travel advice to its citizens traveling to Turkey and has warned that Turkish authorities can arrest tourists for expressing opinions, something which is tolerated in Germany but is not the case in Turkey.

“It cannot be ruled out ... that the Turkish government will take further action against representatives of German media and civil society organizations,” a recent German State Department travel warning said.

“Statements, which are covered by the German legal understanding of the freedom of expression, can lead in Turkey to occupational restrictions and criminal proceedings.”

The travel warning, which was confirmed by a Foreign Ministry spokeswoman, said Saturday that several European journalists, including Germans, have been denied accreditation in Turkey without giving reasons. German citizens have been increasingly arbitrarily detained in the past two years.

The ministry said Turkish authorities were suspicious of any links to the network of U.S.-based Muslim cleric Fethullah Gulen, who Ankara says orchestrated a coup attempt in 2016.

Any tourists who had previously participated in meetings abroad of banned organizations in Turkey face the risk of arrest, as did Germans who said or supported views critical of the Turkish government on social networking sites.