According to the Russian defense ministry, two volunteer soldiers shot at other troops at a Russian military firing range near Ukraine, wounding 11 others and killing 11.
According to reports, the shooting took place in Belgorod in Russia’s southwest which borders on Ukraine.
Moscow’s defense ministry stated that two soldiers from an unnamed ex-Soviet nation opened fire on each other during target practice before they were killed by the return fire.
The incident was deemed terrorist by the ministry.
After President Vladimir Putin ordered an urgent mobilisation to beef-up the Russian forces in Ukraine, the shooting took place.
The defense ministry of Belarus published images earlier showing Russian troops entering Belarus as part of a “regional alliance”.
Photos showed a band performing and female soldiers presenting food to Russian soldiers.
The UK Ministry of Defence stated that many of those being called up by Russia to be in reserve are likely to have to purchase their own body armor.
It stated that the 6B45 vest, which is standard issue, is now available online for 40,000 rubles, an increase of 12,000 rubles in April.
Russia claims that 300,000 reservists have been called up to stop a wave of successful counterattacks by Ukraine. The MoD stated that their equipment was almost certain to be lower than the existing poor supply of troops deployed previously.
Expert assessments have shown that the kit is substandard and many reservists will not be well prepared for combat on the frontline.
Yesterday, President Putin stated that the call-up will be completed in two weeks.
The US also announced that it would send more military vehicles and munitions to Ukraine under a $725m (PS639.7m), package.
This will increase the US total security assistance to Ukraine since February’s invasion by Russia to $17.5bn (PS15.6bn).
According to the US Defence Department, the latest package includes precision-guided artillery and high-speed antiradiation missiles (HARMs).
The support is expected to help Ukraine beat back Russia in its counter-offensive, which has resulted in large territorial gains in the recent weeks.