A prominent Turkish journalist has been attacked outside his home, his newspaper has said, in the latest sign of deteriorating conditions for the media under the president, Recep Tayyip Erdoğan.

Ahmet Hakan, a columnist for Turkey’s leading secular Hürriyet newspaper and a presenter on broadcaster CNN Turk, was followed home from the television station by four men in a black car late on Wednesday, before being assaulted near his residence, according to the Hürriyet editor-in-chief, Sedat Ergin.

“We see that it was an organised, planned attack,” Ergin was quoted as saying. Hakan was treated for a broken nose and ribs, the newspaper said.

The attack comes just weeks after prosecutors launched an investigation into the paper’s owner, Doğan Media Group, for alleged “terrorism propaganda“.

Last month, pro-government mobs attacked Hürriyet offices, accusing the newspaper of sympathising with the banned Kurdistan Workers’ party (PKK) insurgent group.

Hürriyet has been singled out for criticism from Erdoğan as the government struggles to control a surge in Kurdish militant violence in the south-east.

Tensions have been further ratcheted up after Erdoğan’s ruling AK party lost its parliamentary majority in June general elections, and failed coalition talks prompted a snap election, due on 1 November.

In an initial reaction, a senior AKP official denounced the attack. “Turkey is democracy, there is a state of law. We do not approve of or accept this attack,” Ayhan Sefer Üstün said.

In May, Doğan Holding was suspended from state tenders after Erdoğan accused its head, Aydın Doğan, of being a “coup lover” and described its media columnists as “charlatans”.

Turkey has dropped down press freedom league tables under Erdoğan, currently ranking 149th out of 180 in the Reporters Without Borders press freedom index.

On 15 September the group warned of a “dangerous surge in censorship” that threatened to worsen tensions.