"The counter-offensive is the third phase" of Ukraine's plan to retake positions beginning in the south and north, Oleksii Reznikov told French daily Le Monde.

The first phase was an attempt to dissuade Russia from pressing its attack, while the second aimed at "stabilising the front and testing their capacities for resilience".

"Our army chiefs have conceived a plan in function of the weapons we have received from our partners: we started by using the HIMARS mobile artillery systems [from the US] to cut off enemy supply lines and destroy fuel and weapon depots," he said.

France has also recently promised a new package of aid, he said. "I can't give the details but they are very good elements, I'm satisfied."

Ukrainian armed forces say they have recaptured dozens of cities and settlements since the weekend, including the key city of Izyum.

The government also accused Russian forces of targeting the electricity grid as they retreat, causing widescale power cuts in the east.

"This is going to proceed in a series, with episodes: There will be two episodes like this one," Reznikov said.

"It's going to be like a snowball, it's going to start rolling and rolling, getting bigger and bigger... and we're going to see the world's second-largest army forced to retreat."

He reiterated his insistence that a Ukrainian victory would mean a full recovery of territories seized by Russia, including Crimea, annexed by Russia in 2014.

He said Ukraine was also seeking "a clear blueprint for reparations payments by the Russians and the establishment of responsibility for war crimes".