Russia's stated death toll dramatically increased on Wednesday when the the country's defense ministry attributed a fatal missile strike by Ukraine that killed 89 men to the unauthorized use of mobile phones.

The temporary Russian barracks in a vocational college in Makiivka, the twin city of the Russian-occupied regional capital of Donetsk in eastern Ukraine, was reportedly struck by four Ukrainian missiles, according to the Russian defense ministry.

The ministry claimed that despite the official investigation being conducted, servicemen's widespread unauthorized usage of cell phones was the primary cause of the attack.

"This factor allowed the enemy to track and determine the coordinates of the soldiers' location for a missile strike," it said in a statement.

Moscow earlier stated that 63 Russian soldiers were killed in the weekend operation. The ministry's reaction came as some Russian critics became increasingly vocal about what they saw as a half-hearted campaign in Ukraine.

Ukraine's President Volodymyr Zelenskyy made no mention of the incident in a video speech on Tuesday, in which he suggested Russia was planning a huge push to better its fortunes.

"We have no doubt that current masters of Russia will throw everything they have left and everyone they can round up to try to turn the tide of the war and at least delay their defeat," Zelenskyy said in a video address.

"We have to disrupt this Russian scenario. We are preparing for this. The terrorists must lose. Any attempt at their new offensive must fail," he continued.

According to the Ukrainian military, a strike it carried out near Makiivka cost the Russians equipment and probably personnel. But it hasn't provided any more information.

The assault dealt another blow to Putin's so-called "special military operation" to safeguard Russian speakers and prevent threats to Russian security. Moscow is accused by Ukraine and its supporters of making an unwarranted territorial grab.

The situation on the front line close to the eastern town of Bakhmut, according to General Valery Zaluzhny, head of the Ukrainian armed forces, was particularly difficult.

Russian forces have repeatedly attempted to seize Bakhmut and the surrounding territory, in some cases actually marching over the bodies of their own men, according to Zaluzhny, who noted on the Telegram messaging service that Ukrainian forces were holding out.

Zelenskyy reaffirmed Ukrainian claims that Moscow is considering a full-scale mobilization, a step that Russian authorities insist is not being contemplated at the moment.

According to a spokesperson for the U.S. State Department, Washington had received allegations claiming "that the Ukrainian military struck a Russian military barracks that stored ammunition inside of Ukrainian territory" resulting in many Russian deaths.