Russia heavily bombed kyiv on Sunday, killing at least four people, days after a Ukrainian attack on a high school in a Moscow-occupied region that Russian President Vladimir Putin vowed to avenge.

Ukraine detected “690 air attack devices: 90 missiles and 600 drones of different types,” said the air force, which also reported “one intermediate-range ballistic missile.” This is one of the most intense bombings against the city since the start of the Russian invasion four years ago,

According to kyiv Mayor Vitali Klitschko, two people were killed in the capital and 56 were injured. The leader of the kyiv region stated that two people had died in that area, where nine injuries were also reported.

Ukrainian President Volodymyr Zelensky confirmed that the Russian regime launched a nuclear-capable Oreshnik hypersonic missile.

“Three Russian missiles against a water supply facility, a market burned, dozens of residential buildings damaged, several schools,” Zelensky denounced on Telegram. “They are completely crazy,” he said.