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.

White House national security advisor Jake Sullivan hinted Thursday of more sanctions coming against Russia in the "next week or two" aimed at targeting ways Moscow is evading sanctions already imposed.

“Where our focus will be over the course of the coming days is on evasion,” Sullivan said Thursday at the Economic Club of Washington. “As Russia tries to adjust to the fact that it’s under this massive economic pressure, what steps do they take to try to evade our sanctions and how do we crack down on that? And I think we'll have some announcements in the next week or two that identify targets that are trying to facilitate that evasion both inside Russia and beyond."

When Sullivan was asked whether sanctions will automatically be lifted if a negotiated peace deal between Russia and Ukraine is worked out, he appeared cautious with his words, saying, “a lot of that depends on what the shape and scope” of the agreement is.

“A lot of it depends on what the Ukrainians, in consultation with us and the Europeans come to agree to," Sullivan said. "You know, we're not going to do a deal over the head of the Ukrainians where we give a bunch of sanctions relief to Russia. But if some measure of sanctions relief were built in to some credible diplomatic solution led by the Ukrainians, that's something that we would happily discuss."

But Sullivan said Russian oligarchs shouldn't expect to ever get back their yachts and other assets seized under sanctions that have been imposed, saying the ultimate goal is "not to give them back” once the war is over.

“The president is actively looking at how we can deal with the fact that as we seize these assets, our goal is not to give them back. Our goal is to put them to a better use than that," Sullivan said. "But I'll be careful in what I say today because there's an ongoing kind of policy process around how we end up dealing with that question. But, rest assured, that the goal is not just to sit on them for a while."

-ABC News' Justin Gomez