Belar was a Bajoran and part of the Bajoran Resistance during the Occupation of Bajor.
He was on Terok Nor when three Bajorans were executed for attempting to assassinate Dukat. Benjamin Sisko contacted him when Sisko, Odo, and Elim Garak were reliving the past due to a telepathic link created by Odo. Belar was going to arrange passage off the station for the three. As Belar was speaking with Sisko, a bomb went off near Dukat. Belar fled and Sisko was arrested, along with Odo and Garak.
Although not firmly established, Belar's actions seem to indicate that he was part of the plot to kill Dukat. (Deep Space Nine: "Things Past")