Eight people were killed, including a 3-month-old infant, after Russian forces shelled the Black Sea port city of Odesa Saturday, Ukrainian officials said.

"The war started when this baby was 1 month old. Can you imagine what is happening?" Ukrainian President Volodymyr Zelenskyy said during a press briefing. "They are just scum. ... I don't have any other words for it, just scum."

Russian forces fired at least six cruise missiles, Anton Gerashchenko, an adviser to Ukraine's interior minister, said on Telegram. Ukrainian forces were able to shoot down two of the missiles, according to Zelenskyy, who said they were launched by Russian strategic aircraft from the Caspian Sea region.

"Residents of the city heard explosions in different areas," Gerashchenko said in on Facebook. "Residential buildings were hit."

"The only aim of Russian missile strikes on Odesa is terror. Russia must be designated a state sponsor of terrorism and treated accordingly. No business, no contacts, no cultural projects. We need a wall between civilization and barbarians striking peaceful cities with missiles," Ukrainian Foreign Minister Dmytro Kuleba said on Twitter.

Following the airstrike, the Russian Defense Ministry said that the Russian Aerospace Forces were targeting an airfield terminal outside Odesa storing "a large batch of foreign weapons" from the U.S. and European countries.

Ukrainian President Volodymyr Zelenskyy told reporters that U.S. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin will visit Ukraine on Sunday.

Zelenskyy said they will discuss the list of weapons Ukraine needs and their delivery date.

A spokesperson for the State Department declined to comment and a spokesperson for the Defense Department said they had "nothing to offer" on the trip.

-ABC News' Jason Volack

British Prime Minister Boris Johnson told Ukrainian President Volodymyr Zelenskyy that Russia would be held to account for its actions and that the British government is helping collect evidence of war crimes, when the two spoke on Saturday.

Johnson confirmed that the U.K. will provide Ukraine with more defensive military aid including protected mobility vehicles, drones and anti-tank weapons.

He also updated Zelenskyy on new U.K. sanctions against members of the Russian military and confirmed the U.K. would reopen its embassy in Kyiv next week.

Ahead of the U.N. Secretary-General’s meetings with Zelenskyy and Russian President Vladimir Putin, both leaders agreed on the importance of establishing a cease-fire and humanitarian corridor to allow civilians to leave Mariupol, according to a statement from the British government.

The leaders discussed the U.K.'s efforts with partners to reach a long-term security solution for Ukraine, including discussions with international partners to provide more financial support to Ukraine.

Russian forces attacked a steel plant in the shattered Ukrainian port city of Mariupol on Saturday, according to Oleksiy Arestovich, an adviser to the Ukrainian president's office.

In a briefing, Arestovich said Russian forces had resumed airstrikes on the plant and were trying to storm it, a reversal of Russian President Vladimir Putin's order two days earlier.

Ukrainian officials estimate that about 1,000 civilians are sheltered in the plant along with the remaining Ukrainian fighters.

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