Police using tear gas and water cannons raided the headquarters of Turkey's largest-circulation newspaper, hours after a court placed it under the management of trustees.
Officers dispersed protesters who had gathered outside of the opposition Zaman newspaper's Istanbul headquarters before entering the building to escort the court-appointed managers and evict newspaper workers.
The court decision against the newspaper, which is linked to a US-based cleric who is opposed to President Recep Tayyip Erdogan, has heightened concerns over deteriorating press freedoms in Turkey and sparked international outrage.
The legal action came as the government has intensified a campaign against the moderate Islamic movement led by US-based cleric Fethullah Gulen.
It accuses the movement of attempting to bring down the government.
The case was brought by a public prosecutor in Istanbul and meant the editorial board and management were replaced by people named by the court.
The move, which also affects Zaman's sister newspaper, English-language Today's Zaman, and a news agency linked to the group, further reduces the pool of opposition television and newspapers in the country, which is dominated by pro-government television channels and newspapers.
Zaman editor-in-chief Abdulhamit Bilici had addressed his colleagues on the grounds of the newspaper before police stormed the building, calling the court decision a "black day for democracy" in Turkey.
Today's Zaman chief editor, Sevgi Akarcesme, broadcast the police raid on Periscope before police confiscated her phone.
The court decision sparked international outrage.
"I see this as an extremely serious interference with media freedom which should have no place in a democratic society," said Nils Muiznieks, the Council of Europe commissioner for human rights.
"It is the latest in a string of unacceptable and undue restrictions of media freedom in Turkey."
Reporters without Borders issued a strongly-worded statement, accusing Mr Erdogan of "moving from authoritarianism to all-out despotism".
Mr Gulen, who has lived in the United States since 1999, was once Mr Erdogan's ally but the two have fallen out.
The government accuses the Gulen movement of orchestrating corruption allegations in December 2013 against ministers and people close to Mr Erdogan as a plot to overthrow it.
The authorities have since branded the movement a terror organisation, although it is not known to have carried out acts of violence.
Mr Gulen was placed on trial in absentia last year on charges of attempting to topple the government.
The government has cracked down on the movement since, purging civil servants suspected of ties to it, and businesses have been seized.