Many commentators condemn the police action against the Zaman newspaper and Samanyolu TV channel as a clampdown on press freedom. Both are described as being close to Islamic cleric Fethullah Gulen, the spiritual leader of the Hizmet movement, whom Turkish President Recep Tayyip Erdogan accuses of running a "parallel state". Pro-government newspapers, however, defend the authorities' action.
"Hitler also started like this," says opposition leftist daily Taraf. "A strike against democracy," exclaims pro-Gulen newspaper Bugun.
"A raid meant to silence," declares Cumhuriyet. A commentary in the secular daily states that the administration led by President Erdogan "doesn't like anything that is associated with freedom of the press". "It is indisputable that this operation is aimed at strengthening RTE's [Recep Tayyip Erdogan's] authoritarianism and dictatorship," says the article.
"Opposing the raid against Zaman and Samanyolu TV and the detentions does not mean defending their [the Gulen community's] opinions, beliefs and activities. What is at stake here is the freedom of press," argues centre-left daily Radikal.
Zaman, the moderate, pro-Islamic and pro-Gulen daily whose editor in-chief Ekrem Dumanli was detained by the police, has replaced its blue and white masthead with black lettering. "Dark day for democracy," says the paper's headline.
Zaman also runs an article by Mr Dumanli in which he condemns those "who want to turn the country into a spy state and a republic of fear, and want to govern it as if it was their own private fiefdom". "We have a duty to make sure this won't be the case," writes the arrested journalist.
Turkish TV also aired criticism of the arrests. Privately-owned NTV and CNN-Turk showed footage of protesters in front of Zaman's headquarters in Istanbul, holding posters saying, ''We all need free press'' and ''Free media cannot be silenced."
CNN Turk and NTV broadcast critical statements from Kemal Kilicdaroglu, the leader of the main opposition Republican People's Party (CHP). He condemned the police action as a "coup". Mr Kilicdaroglu was also seen on state TRT Haber TV saying that ''if this country's media are not free, then the people will not be free either''.
Pro-government media have largely expressed strong support for the arrests.
All the participants in a studio discussion on pro-Erdogan Kanal 24 TV backed the actions of the authorities, with one of the guests warning that "this is only the beginning", and that new measures were imminent against a "large gang'' made up of subversive elements in the police, the courts, the media and business circles.
"Those who see this as an issue of media freedom know pretty well where the real problem lies," argues pro-government Yeni Safak. The paper states that no journalist should use his position "as a cover for other thingsâ€¦[to] turn journalism into a weapon and make it an extension of the struggle for power".
Referring to last year's corruption allegations against Mr Erdogan, which he says were part of a plot to topple him, pro-government Sabah also points out that "it is time for those who made hundreds of people suffer with fake evidence to account for what they did".
Pro-government Star recalls President Erdogan's promise to end Mr Gulen's alleged "parallel-state structure" and his words that "we will go into their caves". "Their caves have been entered," the daily says in a headline. The Star cautions Mr Erdogan's critics not to make hasty accusations, but rather to wait for the results of the investigation, which will reveal whether Zaman's editor-in-chief was really arrested for his journalistic activities.
BBC Monitoring reports and analyses news from TV, radio, web and print media around the world. You can follow BBC Monitoring on Twitter and Facebook.
The arrest of more than 20 people, many of them from Turkey's media, has ignited a war of words between pro-government and opposition press and TV outlets.