(now a suburb called Starohorodka). In the beginning of the 14th century, a newer settlement arose closer to the Desna, named Oster.

From 1356 Oster was under control of the Grand Duchy of Lithuania, and from 1569 under the Union of Lublin which was part of the Polish-Lithuanian Commonwealth. In 1622, King Jan II Casimir granted Oster the Magdeburg rights