She will reportedly face charges for "discrediting the Russian armed forces", which can carry a prison term of up to 15 years.
Ovsyannikova recorded a video message in Russian before her protest, in which she denounced the war, said her father was Ukrainian, and said she was ashamed of spreading Putin's propaganda.
"What is happening in Ukraine right now is a crime, and Russia is the aggressor country. The responsibility for this aggression lies on the conscience of only one person. This person is Vladimir Putin," she said.
"My father is Ukrainian, my mother is Russian. They have never been enemies. this necklace on my neck is like a symbol of the need for Russia to immediately stop this fratricidal war. Our people can still make peace.
"Unfortunately, during these past years, I have been working at Channel One, involved in Kremlin propaganda. I am very ashamed of this. Ashamed because I allowed lies to be told from the TV screen.
"Right now the whole world has turned away from us. Ten generations of our descendants will not be able to wash off the shame of this fratricidal war.
"We are Russian people. A thinking and smart people. Only we have the power to stop this madness. Go to protests. Do not be afraid. They cannot put us all in jail."
Many thousands of Russians have already been arrested for protesting against the war, including more than 4000 on Sunday alone.
