The Turkish Radio and Television Supreme Council (RTUK) has blocked the websites of German public broadcaster Deutsche Welle over licensing issues.
DW's websites in all its program languages, along with those of international broadcaster Voice Of America, were no longer accessible in Turkey late Thursday.
DW publishes news in 32 languages, including Turkish.
In February, Turkey's media watchdog had called on DW and other international media outlets to apply for broadcasting permits, in line with a 2019 media law, or "face a broadcast ban" and have their websites blocked.
DW said in a statement that it did not comply, as "licensing would have allowed the Turkish government to censor editorial content."
DW Director General Peter Limbourg said: "We had outlined in an extensive correspondence and even in a personal conversation with the chairman of the media control authority why DW could not apply for such a license. For example, media licensed in Turkey are required to delete online content that RTUK interprets as inappropriate. This is simply unacceptable for an independent broadcaster."
"DW will take legal action against the blocking that has now taken place," he added.
German politicians regret the decision
Germany "noted with regret" the Turkish decision to block DW, government spokesperson Steffen Hebestreit told reporters on Friday.
"Our concern about the situation of freedom of expression and of the press in Turkey persists," he added.
The foreign policy spokesman for the opposition Christian Democrats, Jürgen Hardt, said the suspension marked a "new low point" in the "systematic undermining of press freedom" by Turkish President Recep Tayyip Erdogan's government.
"With this decision, Erdogan is putting Turkey in line with countries like China, North Korea and Iran, whose citizens are fundamentally only free to use the internet in ways that suit their government," Hardt said, adding that "Turkey's future" should lie alongside Western countries in values such as the rule of law, liberty, democracy and international solidarity. He said it was to be hoped that "the president of Turkey will indeed recognize this".
DW, alongside other international broadcasters, is one of the few remaining news outlets from which people in Turkey can obtain independent information. In addition to DW, Voice of America and France-based Euronews were also given the notice to apply for a license.
DW had established a liaison office in Turkey in accordance with the 2019 law and has been registered with the relevant Turkish ministry since February 2020.
The 10-member RTUK board is dominated by Erdogan's conservative AKP party and its far-right ally the MHP party.
Turkey has undergone a series of clampdowns on independent and dissenting voices in the media and among academics since a 2016 coup attempt against Erdogan's rule.