The death toll from a Ukrainian strike targeting Russian soldiers in the city of Makiivka has risen to 89, the Russian Defense Ministry said on Wednesday.

"The number of our dead comrades has gone up to 89," Lieutenant General Sergei Sevryukov said in a video statement released by the ministry. More bodies had been found under the rubble in the temporary barracks in the city in Russian-controlled territory, he added.

Ukraine struck the base in Makiivka in the minutes after New Year's Day began, using United States-supplied HIMARS rocket systems, Sevryukov said.

Russian President Vladimir Putin had just delivered his traditional New Year's address when the attack occurred.

On Monday, Russia said that 63 soldiers had been killed in the Makiivka strike — the biggest loss of life from a single attack reported by Moscow since the start of the conflict on Feb 24. It stirred renewed criticism inside Russia of the way the offensive is being conducted.

Kyiv took responsibility for the strike, and the Ukrainian military said the death toll was much higher.

Sevryukov also said on Wednesday that mobile phones used by the soldiers had led to the deadly strike.

"Currently, a commission is working to investigate the circumstances of what has happened," he said.

"But it is already obvious that the main reason ... was the turning on and massive use by personnel of mobile phones within reach of enemy weapons contrary to the ban."

He said measures were being taken to ensure such incidents would not happen in the future, and all those responsible will be punished.

The new announcement came after mourners gathered in several cities of the Volga region of Samara — where some of the servicemen came from — to mourn the dead.

United in grief

At the gathering, Yekaterina Kolotovkina, head of a group of army spouses, said she had asked her husband to "avenge" the victims.

"I haven't slept for 3 days, and Samara hasn't slept, … this is very difficult and scary, But we can't be broken," she told mourners. "We will crush the enemy together. We are left with no choice."

Those in attendance waved flags from pro-Kremlin groups, including the ruling United Russia party. Some 200 people laid roses and wreaths in a central square in the city of Samara as an Orthodox priest recited a prayer.

Similar gatherings were reported in other cities including Tolyatti.

Sevryukov also said that Russia had destroyed Ukraine's multiple launch rocket system used in the attack on Makiivka.

In addition, Russian strikes had destroyed four more HIMARS launchers and killed 200 Ukrainian and foreign mercenaries in the town of Druzhkivka in Donetsk, he said.

Putin has yet to react to the Makiivka attack, which happened during the holiday season before Orthodox Christmas, which many Russians spend with their families.

Agencies via Xinhua contributed to this story.