Ukrainian and Russian forces have been entrenched on opposite sides of the vast waterway in the southern Kherson region for more than a year, after Russia withdrew its troops from the western bank last November.

Ukrainian forces have staged multiple attempts to cross and hold positions on the Russian-controlled side -- with officials in Kyiv finally reporting a "successful" breakthrough last week.

"Preliminary figures vary from three to eight kilometres, depending on the specifics, geography and landscape design of the left bank," army spokeswoman Natalia Gumenyuk told Ukrainian television Sunday, without specifying whether Ukraine's military had complete control of the area or if the Russians had retreated.

"The enemy still continues artillery fire on the right bank," she said, estimating that "several tens of thousands" of Russian troops are in the area.

"We have a lot of work to do," she added.

It comes after Kyiv's much-awaited counteroffensive launched last June had largely fizzled, with Ukraine retaking just a handful of villages in the south and east.

The last significant success claimed by Kyiv was the retaking in August of the village of Robotyne in the southern region of Zaporizhzhia.

A bridgehead on the left bank of the Dnipro could allow a deeper offensive in the south, though it would require deploying more men and armour into the challenging marshy region.

Pushing Russian troops back would also offer protection to Ukrainian towns and villages on the river's western shores that have faced constant shelling over the past year, Ukrainian officials say.

- Drone attacks -

A Russian artillery attack on the city of Kherson injured five people on Sunday, including a three-year-old child, Interior Minister Igor Klymenko said.

Russia's defence ministry said Friday it had thwarted an attempt by Ukrainian troops to land on unspecified islands in the river, days after a Russian-installed official in the occupied Kherson region conceded that Ukraine had managed to hold positions in the village of Krynky on river's eastern shores.

Russia did not comment on the situation on the eastern bank in a daily military briefing on Sunday.

AFP has not able to independently confirm the claims made by officials.

Meanwhile, drone attacks, a defining characteristic of the war, have intensified this week.

Both of the capitals, Kyiv and Moscow, were targeted Saturday night, though both sides claimed to have intercepted most of the attacks and no victims were reported.

Ukrainian drone attacks on Moscow were particularly frequent in the spring, ahead of the launch of its counteroffensive in June, but they have been rare in recent weeks.

Kyiv was also targeted for a second night by a barrage of Iranian-made Shahed drones packed with explosives that were launched by Russian forces, local authorities said.

Russia's defence ministry said its drone attacks hit a fuel depot in Ukraine's central Kirovograd region and an ammunition warehouse near the capital Kyiv.

Ukraine said it shot down 15 of 20 Russian drones, while Russia claimed to have destroyed 31 Ukrainian drones.

- 'Mobile groups' -

Oleksiy Kuleba, the deputy head of President Volodymyr Zelensky's office said Sunday Kyiv was boosting the number of "mobile groups" that could "combat" the wave of Russian drone attacks.

A day earlier, the Ukrainian air force said it had shot down 29 of 38 Shahed drones launched by Russian forces across the country -- the most drones launched by Moscow in an overnight attack since late September.

Saturday night, Ukrainian President Volodymyr Zelensky said he expected Russia to increase its attacks on Ukraine's energy system to paralyse the country's heat and power supply.

"The closer we get to winter, the more Russian attempts will be made to make the strikes more powerful," he said in his daily address, calling on his army to be "100 percent effective, despite all the difficulties, despite all the fatigue".

On the diplomatic front, Russia's Vesti TV announced that President Vladimir Putin will take part in a virtual G20 leaders' summit on Wednesday, after skipping the flagship in-person meeting in New Delhi in September.

Putin has taken few trips outside Russia since the International Criminal Court (ICC) issued an arrest warrant for the Russian leader over the unlawful deportation of Ukrainian children.

The G20 comprises 19 of the world's largest economies plus the European Union and the African Union.