LONDON — A Russian ballistic missile strike on the northeastern Ukrainian city of Sumy killed “many people” on Sunday morning, the city’s acting mayor said, as many there celebrated Palm Sunday.

“The enemy struck the civilian population again,” acting Mayor Artem Kobzar wrote on Telegram.

Andriy Yermak, the head of Ukraine’s presidential office, wrote, “The Russians hit the city of Sumy with missiles, killing civilians.”

This is a developing story. Please check back for updates.