Parents holding babies walked in the street outside the hospital, dazed and sobbing after the rare daylight aerial attack.
Windows had been smashed and panels ripped off, and hundreds of Kyiv residents were helping to clear debris.
"It was scary. I couldn't breathe, I was trying to cover (my baby). I was trying to cover him with this cloth so that he could breathe," Svitlana Kravchenko, 33, told Reuters.
The government proclaimed a day of mourning on Tuesday for one of the worst air attacks of the war, which it said demonstrated that Ukraine urgently needs an upgrade of its air defences from its allies.
Air defences shot down 30 of 38 missiles, the air force said.
Fifty civilian buildings, including residential houses, a business centre and two medical facilities were damaged in Kyiv, the central cities of Kryvyi Rih and Dnipro and two eastern cities, the interior minister said.
An online video obtained by Reuters showed a missile falling from the sky towards the children's hospital followed by a large explosion.
Ukrainian authorities say a Russian Kh-101 cruise missile hit a children's hospital. (AP PHOTO)
The location of the video was verified from visible landmarks.
The Security Service of Ukraine identified the missile as an Kh-101 cruise missile.
Twenty-two people, including two children, were killed in Kyiv and 82 more were wounded in the main missile volley and another strike that came two hours later, officials said.
Eleven were confirmed dead in the Dnipropetrovsk region and 64 were wounded, regional officials said.
Three people were killed in the eastern town of Pokrovsk where missiles hit an industrial facility, the governor said.
President Volodymyr Zelenskiy said Ukraine would retaliate and called on the country's allies to give a firm response to the attack.
"We will retaliate against these people, we will deliver a powerful response from our side to Russia, for sure. The question to our partners is: can they respond?" Zelenskiy who is visiting Poland said during a joint press conference with Polish Prime Minister Donald Tusk.
Diplomats said the United Nations Security Council would meet on Tuesday at the request of the United Kingdom, France, Ecuador, Slovenia and the United States.
The Russian Defence Ministry said its forces had carried out strikes on defence industry targets and aviation bases in Ukraine.
Russia has repeatedly denied targeting civilians and civilian infrastructure, although its attacks have killed thousands of civilians since it launched its invasion in February 2022.
Ukraine's Prosecutor General said he discussed the attacks with International Criminal Court Prosecutor Karim Khan, adding that his office would be sharing evidence with the ICC.
President Volodymyr Zelenskiy says Ukraine will retaliate against Russia over a hospital attack. (AP PHOTO)
The attack came a day before leaders of NATO countries were due to begin a three-day summit of the military alliance that Zelenskiy is expected to attend, with the war in Ukraine one of the focuses.
"This callous aggression - a total disregard for human life, jeopardising European & Transatlantic security - is why leaders will make significant security commitments to Ukraine this week," the US ambassador to Kyiv, Bridget Brink, posted on X.
Ukraine's Defence Minister Rustem Umerov said the missiles flew at extremely low altitudes during Monday's attacks.
DTEK, the largest private power producer, said three electricity substations and networks had been damaged in Kyiv.
Kyiv mayor Vitali Klitschko said the attack was one of the largest of the war, with the damage registered in seven districts across the city.
The health ministery said five units of the children's hospital, the largest and best equipped in the country, were damaged and children were relocated to other facilities.
Meanwhile, two civilians were killed and three more injured after Ukrainian shells hit a village in Russia's Belgorod border region, the governor Vyacheslav Gladkov said on Monday.
Gladkov said one man had died of his wounds in the village of Nikolskoye and another in a nearby hospital.
