BERLIN — Hundreds of private Hungarian news outlets have been simultaneously donated by their owners to a central holding company run by people close to the far-right prime minister Viktor Orban, cementing Mr. Orban’s grip on the Hungarian news media.

If approved by the country’s regulatory authorities, which are led by an official appointed by Mr. Orban, the deal will place most leading private Hungarian outlets under the control of a single, state-friendly entity, in a move that is unprecedented within the European Union, according to Freedom House, a global rights watchdog that analyzes press freedom.

It is the latest broadside against pluralism under the increasingly autocratic Mr. Orban. Since taking power in 2010, he has steadily chipped away at Hungary’s checks and balances, stacking the Constitutional Court with loyalists, reshaping the electoral system to favor his party and placing dozens of watchdog institutions — including the judiciary and prosecution service — under the leadership of his allies.

In coordinated announcements on Wednesday, more than a dozen media owners declared the transfer of — or intention to transfer — over 400 news websites, newspapers, television channels and radio stations to the Central European Press and Media Foundation, a group founded in August that had previously played little role in the Hungarian media. Most of the owners, pro-government business moguls, said they would receive no compensation for the properties.