Ukraine's armed forces have made gains in different parts of eastern Donetsk region, the focal point of Russia's 18-month-old invasion of the country, and in the south, officials said on Sunday.

Ukrainian troops near the front line town of Avdiivka took advantage of Russian forces focusing on one sector to advance and capture part of the village of Opytne south of the city, the head of the local military administration said.

"In my opinion, this is very significant," Vitaliy Barabash told national television. "To be frank, the enemy overlooked this southern direction a bit."

Barabash called the advance a "thunderous assault operation" and said fighting was underway in the settlement.

Avdiivka, site of a major coking plant, has been under near-constant Russian attack for many months.

The General Staff of Ukraine's armed forces reported successes near Bakhmut -- theater of nearly a year of pitched battles until it was captured by Russian troops in May.

In its evening report, the General Staff reported "partial success as a result of assault operations" near Klishchiivka, a village on heights south of Bakhmut -- seen as critical to recapturing the town.

The report also described a measure of success near Robotyne -- a settlement it captured late last month -- as part of its drive southward through Russian-held areas to the Sea of Azov.