TOKYO — It was an unexpected act of protest that shook Japan’s carefully managed media world: Shigeaki Koga, a regular television commentator and fierce critic of the political establishment, abruptly departed from the scripted conversation during a live TV news program to announce that this would be his last day on the show because, as he put it, network executives had succumbed to political pressure for his removal.

“I have suffered intense bashing by the prime minister’s office,” Mr. Koga told his visibly flabbergasted host late last month, saying he had been removed as commentator because of critical statements he had made about Prime Minister Shinzo Abe. Later in the program, Mr. Koga held up a sign that read “I am not Abe,” a play on the slogan of solidarity for journalists slain in January at a French satirical newspaper.

The outburst created a public firestorm, and not only because of the spectacle of Mr. Koga, a dour-faced former top government official, seemingly throwing away his career as a television commentator in front of millions of viewers. His angry show of defiance also focused national attention on the right-leaning government’s increased strong-arming of the news media to reduce critical coverage.

Many journalists and political experts say the Abe government is trying to engineer a fundamental shift in the balance of power between his administration and the news media, using tactics to silence criticism that go beyond anything his predecessors tried and that have frustrated many journalists. These have included more aggressive complaints to the bosses of critical journalists and commentators like Mr. Koga, and more blatant retaliation against outlets that persist in faulting the administration. At the same time, Mr. Abe has tried to win over top media executives and noted journalists with private sushi lunches.