'Massive' barrage of Russian missiles target Ukraine, killing 37 and striking children's hospital

LONDON and KYIV -- At least 37 people were killed -- including three children -- and 170 people were injured across Ukraine on Monday, as Russia launched a barrage of more than 40 missiles, according to President Volodymyr Zelenskyy.

At least five cities fell under attack, including the capital of Kyiv, where 21 people were killed. Okhmatdyt Children's Hospital in Kyiv -- one of the most well-respected children's hospitals in the country -- was damaged along with nearly 100 other facilities including residential homes, kindergartens, a maternity hospital, a college and a business center, according to Zelenskyy.

At least two people were killed in the attack on the hospital, including one female physician. At least seven children were injured, according to officials. Zelenskyy said Monday that doctors, hospital staff and first responders were digging through the debris.

"The entire world must use all its determination to finally put an end to the Russian strikes. Killing is what Putin brings," Zelenskyy said. "Only together can we bring real peace and security."

Ukrainian Minister of Defense Rustem Umerov wrote in a post on Facebook that the Russian attack was "massive" and was carried out "at the peak hour when Ukrainians went to work."

Kyiv city authorities declared July 9 a day of mourning in the capital after the attack, according to a post on Telegram. Meanwhile, Ohmatdyt Children's Hospital asked for donations to help rebuild the hospital after the attack, and raised more than $2 million in just three hours on Monday, according to UNITED24, a fundraising initiative of the President of Ukraine.

The attack, which is among the largest Russian strikes in months, comes a day before U.S. President Joe Biden begins a three-day NATO summit in Washington, where the group is expected to discuss support for Ukraine.

The alliance is expected to make "significant" announcements about increased military and financial support for Ukraine, a senior White House official said last week.

Photos and videos shared by Zelenskyy and those at the hospital appeared to show bloodied doctors carrying out children, a building in the hospital grounds reduced to rubble and the exterior of the main building blown out. One image appears to show young patients sitting on the street with their IVs after the explosion.

A doctor at the hospital told local media the missile destroyed a building where two operations were happening at the time.

The Security Service of Ukraine said in a statement that it had opened a criminal investigation into the strike on the hospital, which it called a "war crime." The service said a Russian Kh-101 missile struck the building, according to its preliminary findings.

At the top of a meeting with U.S. Defense Secretary Lloyd Austin Monday morning at the Pentagon, NATO Secretary General Jens Stoltenberg condemned the recent Russian strikes on Ukraine.

"In Ukraine, Russia continues its brutal war," Stoltenberg said. "Only today we have seen horrendous missile attacks against Ukrainian cities, killing innocent civilians, including children. I condemn these hideous attacks."

The missiles targeted cities including Kyiv, Dnipro, Kryvyi Rih, Slovyansk and Kramatorsk, Zelesnkyy said. At least eight of the dead were in Kyiv, officials said.

At least 10 people were killed and several others injured Monday morning in Russian airstrikes on Kryvyi Rih, a city in central Ukraine and Zelenskyy's hometown, officials said. Another three people were killed in Russian airstrikes on the eastern Ukrainian city of Pokrovsk, officials said.

ABC News' Somayeh Malekian, Matthew Seyler, Joe Simonetti and Morgan Winsor contributed to this report.