Ukraine has liberated an area of over ​​400 square kilometers (155 square miles) in the Kherson region, an army spokesperson said on Thursday.

"Our successes are quite convincing ... More than 400 square kilometers of the Kherson region have already been liberated from the occupiers. And we are moving forward," the state-run Ukrinform news agency quoted Ukrainian southern army command spokesperson Natalia Gumeniuk as saying in an online briefing.

Kherson is one of the four regions Russia has annexed following "sham" referendums denounced by the international community.

Meanwhile, at least three people were killed and 12 others injured in missile attacks by Russian forces, said the Zaporizhzhia Regional Military Administration.

Besides implementing unprecedented sanctions on Moscow, the West has provided Kyiv with heavy weapons, which have allowed the Ukrainian military to advance and reclaim territories taken by Russian forces.

Russia began its "special military operation" in February to "denazify" and "demilitarize" Ukraine.