The Ukrainian army has begun a counterattack along an area in southern Ukraine that had been relatively quiet in recent weeks, moving to keep the Russia’s military off balance even as it makes gains in eastern Ukraine.

The attack in the Kherson region, announced Saturday evening, broke through a Russian line of defence, the military headquarters said in a statement, although it was not possible to independently confirm Ukraine’s assertion.

The attack pushed Russian forces into more unfavourable terrain near the villages of Andriyivka, Lozove and Belihorka, the statement said.

Ukrainian officials have for weeks telegraphed plans to counterattack in the area to threaten Russia’s supply routes into Kherson on bridges over the Dnipro River. But it said the manoeuvre would require the delivery of western artillery systems that had been promised by the US and other allies.

Those weapons are now showing up at frontline positions in the war’s eastern theatre but the military statement made no mention of their use in the announcement of the counterattack in the south.

After Russia’s failure earlier this year to capture Kyiv, the capital, and Kharkiv, Ukraine’s second-largest city, the Russian military has focused its offensive on a slender, about 75-mile frontline in eastern Ukraine’s Donbas region. Elsewhere, the Russian forces have mostly dug into defensive positions.

In the Donbas, Russia’s military last week captured two midsize towns, Svitlodarsk and Lyman. The most intense fighting revolved around the city of Sievierodonetsk, the easternmost city in the Donbas, which is still under Ukrainian control but surrounded on three sides by Russian forces.

Russian troops have been seeking to cut Ukrainian supply line into Sievierodonetsk from the West along a highway and several back roads that the Ukrainians call the “road of life,” since the route is the only means to re-supply their soldiers in the city.

Social media posts on Saturday showed Ukrainian soldiers near burned Russian armoured vehicles on the highway, indicating the Russian military had at least briefly controlled the highway before being rebuffed.

In another indication of how tenuous Ukraine’s hold on Sievierdonetsk has become, street fighting has been raging in the city for days after Russian forces broke into the city, according to officials.