Ukraine's military reported advances and robust defence along the front lines of its 18-month old war with Russia, with Moscow acknowledging "tension" in the southern sector but dismissing Kyiv's campaign as unsuccessful.

Ukraine launched a counter offensive in June to reclaim territory seized by Russia, but has struggled to break through entrenched Russian lines and has faced growing criticism in Western media of concentrating forces in the wrong places.

With Moscow's stretched military resources and dissent in the ranks, however, both sides have measured recent successes by taking control of tiny villages or small pockets of land.

Kyiv has retaken several villages in a southward drive towards the Sea of Azov and says it is regaining ground near the eastern city of Bakhmut, seized by Russia in May after months of battles.

"We are pressing our offensive in the Bakhmut sector and our defenders are advancing confidently metre by metre, namely Klishchivka," Ilya Yevlash, spokesperson for Ukrainian troops in the east told national television.

He was referring to a village located on heights south of Bakhmut, seen as critical to recapturing the city.

Yevlash said Ukrainian troops had withstood an onslaught further north near Lyman, a town they retook last year.

Russian forces had been dealt "a good kick" near the village of Novoyehorivka which halted their advance, he said.

Ukraine's general staff, in its evening report, said its forces were moving towards Melitopol in the south - aimed at severing the land bridge Russian troops have established between Crimea, annexed by Moscow in 2014, and the occupied east.

Russian Defence Minister Sergei Shoigu dismissed the offensive as a failure, while admitting that things were far from easy in parts of southeastern Zaporizhzhia region that Moscow controls.

"Ukraine's armed forces have not achieved their goals on any front," the defence ministry quoted Shoigu as saying.

"The most tense situation is that on the Zaporizhzhia front, The enemy has engaged brigades from its strategic reserve whose personnel have been trained by Western instructors."

Ukrainian analysts said the drive to capture a succession of villages was paying off, but much would depend on pushing on for the next two months before wintry weather takes hold.

Military analyst Serhiy Zgurets, writing on the website of Espreso TV, said the military had opened new fronts in the south with a strategy he dubbed "stretch, attrition and strike".

Ukrainian officials have said in the past week that their forces have managed to push past Russia's first line of defences but now confronted further lines in areas where Moscow has had time to build up fortifications and minefields.

"The enemy is trying to make the most of the 'dry period' to fortify themselves, redeploy and manoeuvre," Natalia Humeniuk, spokesperson for southern forces, told national television.

"They can feel the degree to which we can secure fire control on the logistics routes so important to them."