Firing tear gas and water cannons, Turkish police early on Wednesday raided the Istanbul-based headquarters of a media group critical of the government. The raid comes as the country heads to the polls on November 1 amid concern over authoritarianism.

Media rights groups and the opposition described the raid as a "dark day" and a "coup" against free media in President Recep Tayyip Erdogan's Turkey, who over the past several years has clamped down on opposition media and free speech.

Police clashed with protestors and journalists, several of whom were arrested, as they took over Bugun TV and Kanalturk. The scene was caught on live television as the live broadcast was shut down.

Members of parliament from the main opposition CHP joined the protests and condemned the attack on the media.

Links to controversial Gulen movement

The raid occurred two days after an Ankara court had ruled to seize the assets of Koza-Ipek, a holding company with media assets tied to the US-based preacher Fethullah Gulen, the ally-turned-foe of President Erdogan and his ruling Justice and Development Party (AKP).

Government prosecutors accuse the holding company, one of the country's largest, of financing "terrorism" through its support of the Gulen movement.

Koza-Ipek CEO Akin Ipek dubbed the seizure "politically motivated" and, moments before Bugun TV was shut down, he called in on live television to deliver a message to journalists and viewers not to bow down.

The US-based media rights group Freedom House on Wednesday described the court's decision to take over the holding company as "politically motivated."

"The appointment of managers from pro-government media outlets to head Koza Ipek’s media arm makes clear that the goal is control of public debate," Freedom House said.

The ruling prompted protests and the US Embassy in Ankara also chimed in, tweeting that "When there is a reduction in the range of viewpoints available to citizens, especially before an election, it is a matter of concern."

The EU also criticized the media seizure, with a spokesperson of EU foreign policy chief Federica Mogherini calling the it "alarming" and unbefitting of an EU candidate country.

Friends to enemies

Gulen's Hizmet ("Service") movement had a major falling out after Erdogan tried to close down university prep schools that were supporting it financially.

The global Islamic movement - with influence spread throughout the police, judiciary and media - then revealed a vast corruption scandal in the highest levels of AKP government that threatened to take down Erdogan.

The government responded with a massive crackdown, dismissing hundreds of police, making changes in the judiciary and forcing out or arresting Gulen-affiliated media, while dubbing the movement and its followers "terrorists" and alleging they tried to establish a "parallel" state to carry out a coup.

For years the AKP and Gulen movement enjoyed a strong alliance that enabled the two to "defang" the military and remove its influence from politics, particularly through two "coup" trails against senior military officers based on circumspect and some say fabricated evidence.

Those cases ultimately went to retrial and verdicts against military officers were overturned after Erdogan claimed he had been tricked by the Gulen movement, and the AKP and Gulen became embroiled in their own intra-Islamist fighting.