Since the commencement of its counterassault against Russia in late August, Ukraine has reclaimed roughly 1,170 square kilometers (450 square miles) of land in its southern Kherson area, a military official said on Sunday.

Ukraine’s attack in the north-east was a resounding success, but its push in the south to eliminate a Russian foothold on the west bank of the wide Dnipro River has been a slower and more laborious affair.

Southern military command spokesperson Natalia Humeniuk said that Ukraine was making progress on the Kherson front, but that lots needed to be done to secure newly recaptured territories.

“Work is continuing on consolidation of territory, clearing it and conducting stabilizing operations, as the settlements we enter contain many surprises left by the (Russian) occupiers,” she said on Ukrainian national television.

“As of today, from the beginning of the counter-offensive, over 1,170 square kilometers have been liberated in the Kherson direction,” Humeniuk said.

Ukrainian officials have long talked up the priority of recapturing Kherson, a flat, agricultural region which Moscow captured in its near entirety in the early days of its invasion.

Any major territorial losses in Kherson would threaten Russia’s supply lines to the strategically significant Crimean Peninsula further south, the return of which Kyiv has coveted since its occupation by Russia in 2014.