(Reuters) - Russia's defence ministry on Wednesday blamed mobile phone use by its soldiers for a deadly Ukrainian missile strike that it said killed 89 servicemen, raising the reported death toll from 63.

The New Year's Eve strike, the deadliest single incident Moscow has acknowledged since the start of the war, has angered pro-war Russian commentators, increasingly vocal about what they see as a half-hearted and incompetent campaign in Ukraine.

Criticism has been directed at military commanders rather than Russian President Vladimir Putin, who has not commented publicly on the attack, which has dealt a further blow after major battlefield retreats in recent months.

The Russian defence ministry said four Ukrainian rockets had hit a temporary Russian barracks in a vocational college in Makiivka, twin city of the Russian-occupied regional capital of Donetsk in eastern Ukraine.

Although a probe has been launched, the Russian ministry said the main reason for the attack was the mass use of mobile phones by servicemen, which it described as illegal.

"This factor allowed the enemy to track and determine the coordinates of the soldiers' location for a missile strike," it said in a statement issued just after 1 a.m. (2200 GMT Tuesday) on Wednesday.

Russia has effectively shut down all direct opposition to the war, with open criticism banned by severe media rules. But it has given comparatively free rein to pro-war nationalist bloggers, many with hundreds of thousands of followers on social media.

Semyon Pegov, a war correspondent awarded the Order of Courage by Putin, said on Telegram that pointing the finger at troops using mobile phones "looks like an outright attempt to smear the blame". There were other ways Ukraine could have spotted the base, he said.

Pegov said the death toll would rise further: "The announced data is most likely for those who were immediately identified. The list of the missing, unfortunately, is noticeably longer."

Ukrainian President Volodymyr Zelenskiy, who rarely comments on specific Ukrainian military strikes, made no mention of the attack in a video address on Tuesday.

Ukraine initially said hundreds of Russians were killed in Makiivka. It has since avoided giving details.