A prominent Russian TV journalist said Friday she has been barred from anchoring her analytical news show in what is seen by critics as a government attempt to silence a television station.

Olga Romanova was the star news presenter on the nightly program 24, which in recent years was seen as the last TV broadcast still free from state control.

But when she arrived for work on Thursday, security guards barred her from entering the studio.

She says the men were not from the TV station, but said they had orders to keep her out. They asked her to give them a certificate stating she was ill, but she replied she was perfectly healthy and ready to go on the air.

Ms. Romanova's program was carried on REN-TV, a channel that broadcast mostly to Moscow and its surrounding region.

Ren-TV's general director denied there was anything political in the decision to take her off the air, saying it all had to do with falling ratings for her program.

But when the channel's majority interest was sold earlier this year to two companies linked to the Kremlin, analysts said it was only a matter of time before it would follow most other networks and fall under some degree of state control, even if indirectly.

Alexander Petrov is deputy head of the Moscow branch of the watchdog organization, Human Rights Watch.

He says the channels have all become just like one another, in the tone of their commentaries and the way they are presented. He says it is hard to distinguish one channel from another, that this is part of what the government calls "building vertical power." But he sees no logical or reasonable explanation for this.

Under President Vladimir Putin, all major Russian broadcasters have gradually come under direct or indirect state control, usually after being sold to owners or businesses tied to the Kremlin.

In each case, the new owners pledged that editorial independence would be respected. However it was not long before critical journalists either quit or were forced to resign.

Ms. Romanova says she has received calls of support from many of her colleagues.

Frederick Yakovenko of the Russian Journalist's Union told reporters Friday that the Ren-TV case "closes the last air hole for nationwide political broadcasts, which are now encased in concrete."

Many major newspapers in Moscow remain independent, but, in the past year, some have also fallen victim to the same process.