Russia has fired senior military commanders in recent weeks "who are considered to have performed poorly during the opening stages of its invasion of Ukraine," the U.K. Ministry of Defense said Thursday in an intelligence update.

According to the ministry, Lt. Gen. Serhiy Kisel, who commanded Russia's elite 1st Guards Tank Army, has been suspended for his failure to capture Ukraine's second-largest city, Kharkiv. Vice Adm. Igor Osipov, who commanded Russia's Black Sea Fleet, has also likely been suspended following the sinking of the fleet's flagship, Moskva, in April. Gen. Valeriy Gerasimov, the Russian military's chief of the general staff, likely remains in his post, but it was unclear whether he retains the confidence of Russian President Vladimir Putin, according to the ministry.

"A culture of cover-ups and scape-goating is probably prevalent within the Russian military and security system," the ministry said. "Many officials involved in the invasion of Ukraine will likely be increasingly distracted by efforts to avoid personal culpability for Russia’s operational set-backs."

"This will likely place further strain on Russia's centralised model of command and control, as officers increasingly seek to defer key decisions to their superiors," the ministry added. "It will be difficult for Russia to regain the initiative under these conditions."

Russia has placed two Ukrainian commanders on a wanted list.

Serhiy Velychko and Kostiantyn Nemychev, commanders of the Azov Regiment, a far-right group now part of the Ukrainian military, have been added to the Russian Ministry of Internal Affairs' database of wanted fugitives in connection with a criminal case.

According to the Russian Investigative Committee, Velychko and Nemychev are accused of attempted murder of at least eight Russian servicemen who sustained multiple injuries in eastern Ukraine's Kharkiv region. Criminal charges were brought against the pair in absentia, and Russian authorities are working to track down and apprehend them.

The Senate on Wednesday night unanimously confirmed the new U.S. ambassador to Ukraine, Bridget Brink, a career foreign service officer.

The vote took place on the same day the U.S. officially resumed operations at its embassy in Kyiv.

-ABC News' Trish Turner

Google Russia has published a notice of its intention to file for bankruptcy, a spokesperson told ABC News in a statement.

"We previously announced that we paused the vast majority of our commercial operations in Russia. The Russian authorities’ seizure of Google Russia’s bank account has made it untenable for our Russia office to function, including employing and paying Russia-based employees, paying suppliers and vendors, and meeting other financial obligations," a Google spokesperson said.

Adding, "People in Russia rely on our services to access quality information and we’ll continue to keep free services such as Search, YouTube, Gmail, Maps, Android and Play available."

-ABC News' Rashid Haddou-Riffi

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan