Earlier this month it posted results from one hole at this zone, which showed 22.2m (metres) at 2.62 g/t (grams per ton) of the yellow metal.
Today, the firm said it had received assays for more holes, and said the drill-proven strike length of mineralisation at zone 23 is now more than 600 metres, with assays received for six sections over a strike length of 400m and to a depth of 150m to 250m, averaging 1.86 g/t (grams per ton) gold over a combined drill width of 24.96 m (meters) in two stockworks.
The company aims to deliver a maiden resource estimate by the fourth quarter of 2018.
"Zone 23 is a major building block of Orsu's maiden mineral resource statement expected in the fourth quarter of 2018," said Dr. Sergey V. Kurzin, executive chairman of Orsu.
"As the company reported earlier, we expected that we might be able to extend the Main and Southern stockworks at zone 23."
Director of exploration, Dr Alexander Yakubchuk, said: "Orsu successfully extended the gold mineralization both westward and eastward at zone 23. Both stockworks remain open downdip and to the west of Section 9220E, where Orsu has already drilled two drill fences up to the westernmost Section 9010."
The Sergeevskoe gold project licence occurs immediately east from the Alexandrovskoe open pit and gold plant owned by Zapadnaya Gold Mining Ltd, and to the west from the Klyuchevskoe gold licence owned by Sun Gold Mining.
The Klyuchevskoe (Klyuchi) gold deposit represents a plus-six-million-ounce gold endowment. Orsu owns a 90% interest in the Sergeevskoe gold project.
Shares gained over 13% to stand at C$0.21.