Its forces are also trying to advance southward to the Sea of Azov to sever a land bridge established by Russia between the annexed Crimean Peninsula and positions it holds in the east.

Ilia Yevlash, a spokesperson for Ukraine’s eastern group of forces, told national television: “We continue to repel intense enemy attacks near Klishchiivka and Andriivka.

“The enemy is still storming these positions with the hope of recapturing lost positions, but without success.”

There had been 544 Russian shelling incidents in the past 24 hours in the area, seven combat clashes and four air attacks, Yevlash said.

President Volodymyr Zelenskiy referred briefly in a post on the Telegram messaging app to “our advance in the Donetsk sector” in the east, but provided no details.

Ukraine’s General Staff reported air strikes on four localities in the area and said 15 towns and villages had come under artillery and mortar attack.

In its account of military activity, Russia’s Defence Ministry also reported heavy fighting in the area, saying its forces had beaten back 10 attacks by Ukrainian troops near Klishchiivka and further south, near the village of Nevelske.

Ukrainian officials have spoken of gains in the drive southward, with General Oleksandr Tarnavskyi, commander of forces in the south, telling CNN last week of a “breakthrough”, while noting that progress was slower than had been hoped.

Zelenskiy and other officials have said the counteroffensive will take time and have dismissed Western critics who said the advance has been too slow and beset by strategic errors.

Tarnavskyi referred to the village of Verbove, which other officials have said Ukrainian forces are poised to seize. Ukrainian forces are targeting several other villages as they progress through Zaporizhzhia region towards the major town of Tokmak.

“There have been three or four days of painstaking hard work by our assault group and commanders conducting tactical tasks in this area which have led to very serious problems for the Russians,” military analyst Roman Svitan told NV Radio.

“I would not speak of a breakthrough until we reach Tokmak.”

(Reporting by Ron Popeski and Maria Starkov; Editing by Jamie Freed)