The Pentagon has no reason to doubt reports that submarine-launched missiles were used in Russia's missile attack on Vinnytsia on Thursday, a senior U.S. military official told reporters.

The attack killed 23 people, including three children.

The Pentagon has no sign of a military target in the area that Russia could have been aiming for, the official said.

"That looked like an apartment building," the official said, adding there's "no indication" of a military target "anywhere near that."

The official estimated, based on open-source reporting, that 100 to 150 civilians have been killed by Russian strikes over the last two weeks.

-ABC News’ Matt Seyler

The grandmother of a 4-year-old girl killed in Thursday’s Russian missile attack in Vinnytsia told ABC News, “They took the most precious [person] I had in my life.”

Four-year-old Liza was among 23 people, including three children, killed in the strike.

Liza’s grandmother, Larysa Dmytryshyna, called her a “wonderfully sunny child.”

"She was the most wonderful girl in the world and it is so painful that her mother cannot even bury her,” she said.

Asked how she feels about Russia, Dmytryshyna, replied, "I hate them all.”

"We did not ask them to come here. They have caused so much sorrow,” she said of the Russians. "I would give my own life to extinguish the entire country.”

-ABC News’ Tom Soufi Burridge, Ibtissem Guenfoud and Natalya Kushnir

One of Ukraine's leading medical experts on developing prosthetic limbs for amputees says there has been a dramatic surge in demand for artificial arms and legs since Russia invaded Ukraine.

Dr. Oleksandr Stetsenko told ABC News that financial support or donations of prosthetic parts are needed from abroad to meet the increased demand.

External support, he said, is vital so that people have the chance to continue with their lives.

"With good prosthetics people can come back to life again," Stetsenko told ABC News.

There is currently no official figure for how many people in Ukraine have undergone surgery to remove limbs because of injuries sustained from the war but Dr. Stetsenko estimates that around 500 people have had limbs amputated since the end of February with the majority of those cases being soldiers and around a fifth being civilians.

While the number of patients in Ukraine needing artificial limbs has increased, the domestic supply of components to make prosthetic arms and legs has reduced.

That is because a third of the companies which were previously producing components in Ukraine are now located in territory which has recently been occupied by Russian forces or in areas near to the frontline, according to the Ukrainian Ministry of Health.

A director at the health ministry, Oleksandra Mashkevych, confirmed that Ukraine is no longer able "to cover all of the demand relating to artificial limbs."

Mashkevych told ABC News that children who need artificial limbs are sent abroad to Europe or to the United States and that around 20 children in Ukraine are thought to have had limbs amputated since the start of the war in February.

-ABC News' Tom Soufi Burridge, Ibtissem Guenfoud, Natalya Kushnir and Kuba Kaminski

At least 18 people are still missing after a deadly missile strike on downtown Vinnytsia in central Ukraine on Thursday, the Ukrainian National Police said.

Three Russian Kalibr missiles launched from a submarine struck an office building and damaged nearby residential buildings in Vinnytsia, located about 155 miles southwest of the Ukrainian capital, Kyiv, on Thursday morning.

At least 23 people -- including 3 children -- died in the attack, Ukraine's State Emergency Service said, and more than a 100 were wounded, some critically.

The bodies of 2 children and 11 adults were yet to be identified on Friday morning, local authorities said.

The strike in the heart of Vinnytsia is “part of a systematic Russian campaign of attacks on residential areas of cities in Ukraine”, the Institute for the Study of War said.

The search continued on Friday morning for at least 18 people who were still missing after the attack. The ongoing rescue operation has been unprecedented in its scale, local officials said, with more than 1,000 rescuers and 200 pieces of equipment being involved in clearing the rubble and searching for those still missing.

Several dozen people were reportedly detained in Vinnytsia on Thursday for questioning under the suspicion of acting as local spotters or aimers on the ground for the Russian strikes.

The eastern city of Mykolaiv also reported 10 powerful explosions on Friday morning. The city's two biggest universities were hit in the attack, wounding at least four people, local authorities said. Russia also struck a hotel and a shopping mall in Mykolaiv on Thursday.

Russian shelling also targeted Kharkiv, another eastern city, on Thursday night. Local officials claimed 2 schools were damaged in the attack.

The European Union and the United Nations strongly condemned Russia for what the EU called a “long series of brutal attacks against civilians."

Russia's missile strikes hit more than 17,000 facilities of civilian infrastructure as opposed to around 300 military facilities since the start of the war, Ukrainian officials said on Thursday.

-ABC News' Edward Szekeres, Yulia Drozd, Fidel Pavlenko and Yuriy Zaliznyak