Russian President Vladimir Putin's comments Thursday morning claiming victory in Mariupol was "yet more disinformation" from Russia's "well-worn playbook," State Department spokesperson Ned Price told reporters.

Price called Putin's comments an attempt to "distract from what can only be considered the underperformance of Russia's military forces and its failure to achieve its original objectives in Ukraine."

Price said Ukrainian forces in Mariupol "continue to hold their ground."

"Their ferocious stand stands in stark contrast to the plummeting morale that we've seen among Russia's forces. It stands in stark contrast to the tactics that we've seen Russia impose against those in Mariupol," he added.

Price said the U.S. has called for humanitarian access -- aid to get in and people to get out -- and has supported humanitarian groups working to do so. But he blamed Russia's attacks on humanitarian corridors for preventing it from happening.

-ABC News' Conor Finnegan

The U.S. has assessed that the Ukrainian port city of Mariupol remains contested, and that Russian airstrike activity remains focused there and on the Donbas region, a senior U.S. defense official said Thursday.

Russia now has 85 battalion tactical groups, each made up of roughly 800 to 1,000 troops, inside of Ukraine, the official said. More of these groups are headed to the Donbas region, the official said.

-ABC News' Luis Martinez

Mariupol Mayor Vadym Boychenko told ABC News he thinks his city will hold out, saying Russian forces have "been fighting our boys for 57 days and they still can’t win."

The mayor's comments come hours after Russian President Vladimir Putin declared that his siege of Mariupol had been a success, congratulating his defense minister and thanking Russian troops. Putin also ordered troops to abandon their assault on the Azovstal Iron and Steel Works plant, the last holdout for Ukrainian troops in the port city.

Boychenko said 100,00 civilians remain, including 1,000 in the steel plant.

President Joe Biden also pushed back on Putin's claim that Russia has control over Mariupol, saying at a news conference Thursday, "There is no evidence yet that Mariupol has completely fallen."

-ABC News' James Longman

Ukrainian Deputy Prime Minister Iryna Vereshchuk said 19 Ukrainians, 10 military and nine civilians, have been released from Russian captivity in the second prisoner swap this week.

-ABC News' Alexandra Faul

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