Ukraine’s armed forces have halted a Russian offensive towards the cities of Kupiansk and Lyman in the east of the country, and are advancing in the south, a senior Ukrainian defence official said on Friday.

“We had very fierce battles in the Kupiansk and Lyman directions, but our soldiers stopped the enemy there,” Deputy Defence Minister Hanna Maliar told Ukrainian television.

Ukraine is in the early stages of its most ambitious counterattack since Russia’s full-scale invasion in February 2022 and says it has retaken eight villages, its first substantial gains on the battlefield for seven months.

But Russia still holds swathes of territory in eastern and southern Ukraine, and Ukrainian forces have yet to push to the main defensive lines that Russia has had months to prepare.

“Indeed, we still have the main events ahead of us. And the main blow is still to come. Indeed, some of the reserves - these are staged things - will be activated later,” Maliar said.

She said Russian forces still aimed to gain control of the whole of the Donetsk and Luhansk regions in eastern Ukraine.

Ukraine’s military operation in the south was going according to plan and its forces were advancing, even if minefields were slowing them down, she said.

“In the military, according to their reports and positions, everything is moving according to plan. It is not necessary to expect the offensive to be something very fast,” Maliar said.

“Every day we are advancing, every day. Yes, it is gradual, but our forces are gaining a foothold on these borders and they are advancing steadily.”

Reuters was unable to verify the situation on the battlefield. Each side says the other has suffered heavy losses since Ukraine began its counteroffensive, and Moscow has not acknowledged Ukraine’s recent military gains.