[1] With the beginning of the 1972–1973 Ukrainian purge, the leaders of the Sixtier were arrested and reform-minded Petro Shelest was removed as First Secretary of the Communist Party of Ukraine.

After hearing about the founding of the Ukrainian Helsinki Group in a Radio Liberty broadcast, Ovsienko spread the news to close friends.

Ovsienko was charged with resisting arrest, including insulting an officer and ripping two buttons from his jacket, and sentenced to three years' imprisonment.

Ovsienko was urged to write a statement providing grounds for a pardon, but refused (along with several other political prisoners) out of the belief that he had been wrongfully convicted.

He was pardoned a year later in spite of his refusal to write a statement, being among the final five to be released (alongside Mykola Horbal, Ivan Kandyba, M. Alekseyev, and Enn Tarto).

[2] He returned to Perm-36 a year later to participate in the reburials of Vasyl Stus, Yuriy Lytvyn, and Oleksa Tykhy, who had all died during their sentences at the prison.

However, he failed to establish a chapter of the Helsinki Group or the People's Movement of Ukraine in his native village.

[2] In the late 1990s he organised expeditions to Sandarmokh and the Solovetsky Islands, where mass killings had occurred during the Great Purge.

In the early 2000s, along with Yevgen Zakharov, Ovsienko wrote a four-volume compendium of dissidents in the Eastern Bloc, including around 200 Ukrainian political prisoners.