The cause of the crash, which comes as the country's war with Russia approaches the 11-month mark, was not immediately clear.
At least nine of those killed had been onboard the emergency services helicopter when it crashed in Brovary, a suburb about 15 miles northeast of the capital, Ihor Klymenko, the head of the national police, said in a statement.
He said the dead included Ukrainian Interior Minister Denys Monastyrsky, his deputy, Yevhen Yenin, and Yurii Lubkovych, the state secretary. One child was also among the dead, officials said.
Officials had earlier put the death toll at 18, including four children, but it was later revised down as authorities stressed the final figure was uncertain.
"The pain is unbearable," President Volodymyr Zelenskyy said.
"May all those whose lives were taken this black morning rest in peace!” he said in a statement.
At least 25 people, including 11 children, were being treated in hospitals, officials said. The extent of their injuries was not immediately clear.
The helicopter fell near a kindergarten and a residential building, according to Oleksii Kuleba, the head of the Kyiv Regional Military Administration.
"At the time of the tragedy, children and employees of the institution were in the kindergarten. At this point, everyone was evacuated," he said.
Video and photos shared online by Ukrainian officials showed flames bursting from at least one building as smoke billowed from the crash site.
The Security Service of Ukraine said on its Telegram channel that it was considering at least three possible causes, including malfunction, a violation of flight rules or “deliberate actions to destroy the vehicle.”
Prime Minister Denys Shmyhal said he had ordered a special commission to be created to lead an investigation.
Yurii Ihnat, a spokesperson for Ukraine’s Air Force Command, said the commission would include a number of aviation experts. "It is too early to talk about the causes of the crash," he said, speaking during a national telethon.
A senior police official in the Kharkiv region said the helicopter was due to travel to the area in the country's northeast when it crashed.
There has been no fighting reported around Kyiv for months after Russian forces pulled back from the region following a failed assault on the capital.
Officials in Ukraine and across Europe paid tributes to the dead.
“Tragedy far from the frontline, in Brovary,” Ukrainian Foreign Minister Dmytro Kuleba said on Twitter.
“I wish a speedy recovery to those injured. Denys Monastyrskyi and Yevhenii Yenin were close colleagues & friends of mine, true Ukrainian patriots. Huge loss for all of us,” he said.
Shmyhal said it was “a great loss for the government team and the entire state."
"My sincere condolences to the families of all the victims," he said.
“My colleagues, my friends. What a tragic loss,” Interior Ministry adviser Anton Gerashchenko wrote in a tweet. “Deepest condolences to their families.”
Ukrainian first lady Olena Zelenska could also be seen dabbing away tears Wednesday morning before attending a World Economic Forum session in Davos, Switzerland, according to The Associated Press.
Forum President Borge Brende asked for 15 seconds of silence after opening the session to honor the Ukrainian officials killed in the crash.
The U.S. ambassador to Ukraine, Bridget A. Brink, said on Twitter that she was "shocked and saddened by the terrible news from Brovary."
Charles Michel, president of the European Council, remembered Monastyrsky as a "great friend of the EU."