At least 18 people were killed, including Ukraine’s interior minister and three children, after a helicopter crashed near a kindergarten on the outskirts of Kyiv on Wednesday morning.

The cause of the accident, which comes as the country’s war with Russia nears the 11-month mark, was not immediately clear.

At least nine of the dead were aboard the emergency services helicopter when it crashed in Brovary, a suburb about 15 miles northeast of the capital, national police chief Ihor Klymenko said in a statement.

Among the dead were Ukraine’s Interior Minister Denys Monastyrsky, his deputy Yevhen Yenin, and State Secretary Yurii Lubkovych, Klymenko said.

Interior Minister of Ukraine Denys Monastyrsky. Sergei Supinsky / AFP – File Getty Images

At least 29 people, including 15 children, were being treated in hospitals, said Oleksii Kuleba, head of the Kyiv Regional Military Administration. The extent of his injuries was not immediately clear.

Kuleba said the helicopter fell near a kindergarten and a residential building.

«At the time of the tragedy, the children and the employees of the institution were in the kindergarten. At that time, they were all evacuated,» Kuleba said.

Ukrainian officials paid tribute to their colleagues.

“My colleagues, my friends. What a tragic loss,» wrote Interior Ministry adviser Anton Gerashchenko in a cheep. «My deepest condolences to their families.»

This is a developing story. Please check for updates.

Artem Grudinin, darina mayer Y mahalia dobson contributed.