"Today there was a powerful artillery attack on enemy positions in ... the entire territory of the occupied Kherson region," Sergey Khlan, a local deputy and adviser to the regional governor told Ukraine's Pryamyi TV channel.

"This is the announcement of what we have been waiting for since the spring -- it is the beginning of the de-occupation of Kherson region."

Russian forces seized Kherson on March 3.

It was the first major city to fall following Moscow's invasion of Ukraine on February 24.

Khlan said Ukrainian troops now had "the advantage" on the southern front. Several strikes in recent weeks have targeted bridges in the region, in a bid to hamper logistics for the Russian military.

Ukrainian media had earlier quoted southern army command spokeswoman Natalia Gumeniuk as saying Kyiv's forces were attacking the front from "many directions".

On Facebook, the "Kakhova" Ukrainian military group said it had seen "the retreat" of pro-Russian separatist fighters from their positions in the region.

None of these claims could be immediately verified by independent sources.

Kherson is the main city in the region of the same name. The region is important for Ukrainian agriculture and is adjacent to the Crimean Peninsula, which Russia annexed in 2014.

In late July, Khlan said the region would be recaptured by Kyiv's forces by September.