General Syrsky confirmed on Sunday that Russia had made some “tactical” progress in that part of the front, but said Moscow had not yet achieved what he called an “operational advantage”.

He also said additional units were being deployed to replace those that had sustained heavy losses.

The recent setbacks have prompted rare criticism from Ukraine’s military bloggers.

“The (Russian) breakthrough near Ocheretyne revealed a number of problems,” the Deep State Telegram channel, with close links to the Ukrainian army, said in a post on Wednesday.

It said leaders of the 115th mechanised brigade, which is fighting in the area, were “responsible for the collapse of the defence in the entire sector, allowing significant losses”.

Kyiv’s forces are outnumbered across the battlefield, with the country struggling to recruit enough soldiers to replace those who have been killed, wounded or exhausted by the war, now in its third year.

Leaders in Kyiv have warned the military outlook could worsen in the next few weeks, while shipments of US weapons are making their way to the front lines.

Kyrylo Budanov, Ukraine’s head of intelligence at the ministry of defence, said this month that the battlefield situation would likely be at its most difficult in mid-May to early June.