Russian troops were moving new units as they were ready to attack Slovyansk from both Russian-controlled Izyum, a city about 50 kilometres to the north.

The recently captured small town of Lyman, the General Staff’s daily situation report said.

Moscow has been pouring its military resources into eastern Ukraine for weeks and, in spite of heavy resistance from Ukrainian forces, Russia has slowly gained ground.

Slovyansk and Kramatorsk, which sits just to the south, is the largest urban area in the Donbas still under Kiev’s control.

Slovyansk is also the base for Ukrainian armed forces in the country’s east.

Russian seizure of the twin cities would mark a significant turning point in the war.

According to the Ukrainian side, Russia has moved 250 military vehicles to the Izyum area and repaired a damaged rail bridge to speed up supply lines.

In addition, the General Staff said a squadron of Ka-52 attack helicopters had also been deployed north of Izyum.

The Ka-52s was considered Russia’s most advanced heavy attack helicopters.

In addition to Slovyansk, the area between Severodonetsk and Lysychansk continued to be the focus of Russian efforts in the Donbas.

Kiev said Moscow was focusing on cutting Ukrainian supply lines near Severodonetsk.

Severodonetsk had been the target of Russian attacks for months and was considered the largest Donbas city still held by Ukraine.