The Russian Defence Ministry on Friday began sending reinforcements to the eastern Ukrainian region of Kharkov, where, according to Kiev, Ukrainian forces are advancing and recapturing territory in a counteroffensive.
A defence video, shown on Russian state television, shows convoys of armoured vehicles, trucks and special equipment heading, according to Moscow, to the Kharkov front.
According to Rossiya-24, Mi-26 helicopters carrying troops and equipment to the towns of Kupiansk and Izium are also involved in the transfer of reinforcements.
Kupiansk is about 118 kilometres from the city of Kharkov, which Russia never managed to seize in the seven-month war, and is a key logistical hub for Moscow, supporting the land lines of communication on the Izium axis, which is controlled by Russian troops.
The Russian TV channel claims that the aircraft land practically on the line of contact between Russian and Ukrainian forces.
The Kremlin on Friday declined to comment on reports of the Ukrainian counteroffensive and redirected the question to the Russian Defence Ministry.
At the same time, the pro-Russian administration in Kharkov, a region where Moscow's troops control 20% of the territory, announced that the population in some areas is being evacuated because of a "complicated and ambiguous" situation on the front line.
According to the morning war report of the General Staff of the Armed Forces of Ukraine, in the Kharkov region the counteroffensive has advanced almost 50 kilometres in three days.
The day before, it reported that more than 20 localities had been liberated from Russian occupation in this province.
According to Ukrainian President Volodymir Zelensky, Ukrainian troops have regained control over 1,000 square kilometres in the south and east of the country since 1 September.