Previously, Vladimir Putin claimed that the Russian military will never deploy young men into the warzone that had been recently drafted into the army amid a shortage of troops.
Moscow had said that only professional soldiers and officers were fighting in the invasion of Ukraine, which started on 24 February.
But, on 9 March, a member of the Russian Federation Council said that Russia was sending conscripts to fight in Ukraine, and that only four members of a 100-unit company survived.
Two days prior, Mr Putin told women in Russia that he would not send young male reservists and conscripts to war.
On Tuesday, Artur Yegiyev – military prosecutor of the Western District of Russia – told Russia’s upper house of parliament that 600 conscripts had been “mistakenly” sent to Ukraine.
He added that 12 officials, who he said had been responsible for the deployment of conscripts, are being put through a disciplinary process and could face dismissal.
The conscripts had “returned [to Russia] as soon as possible”, Mr Yegiyev also told the Federation Council.
Russia has stopped publishing statistics about how many of its soldiers have died in Ukraine, but estimates have run into the thousands.
Some associations representing mothers of Russian soldiers have raised concerns about conscripts being drafted to fight despite a lack of adequate training. All sides in the Ukraine conflict have systems of conscription, where young men are required by law to do military service.
Meanwhile, Russia has claimed that it has occupied large swathes of eastern Ukraine after a relentless, weeks-long barrage and the recent deployment of more troops.
Russian defence minister Sergei Shoigu said Moscow’s forces have “liberated” 97 per cent of the Luhansk region.
Russia appears determined to capture the Donbas region of eastern Ukraine, which is made up of Luhansk and Donetsk.
Mr Shoigu claimed that Russian forces have seized the residential quarters of Severodonetsk and are fighting to take control of an industrial zone on its outskirts and the nearby towns.
He added that the Russian troops were pressing their offensive toward the town of Popasna – about 20 miles south of Severodonetsk – and noted that they have taken control of Lyman and Sviatohirsk and 15 other towns in the area.
A Ukrainian official said that Moscow is deploying troop reinforcements in eastern Ukraine as a Russian artillery barrage had been aiming to grind down Ukrainian defences.
Luhansk governor Serhiy Haidai conceded that Russian forces control the industrial outskirts of Severodonetsk, one of two cities in the Luhansk region still in Ukrainian hands.
“Toughest street battles continue, with varying degrees of success,” Mr Haidai told The Associated Press. “The situation constantly changes, but the Ukrainians are repelling attacks.”
Moscow, which sent thousands of troops into Ukraine, has said that it is engaged in a “special military operation” to demilitarise its neighbouring country and rid it of dangerous nationalists threatening its Russian-speaking population.
Ukraine and its allies dismiss Russia’s claims as a baseless pretext to launch an unprovoked war of aggression that has killed thousands, flattened cities, and driven more than 6 million people to flee abroad.
Additional reporting by Reuters and AP